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ESSENTIALS OF PHYSICS LABORATORY TRAINING
Presentation · April 2011
DOI: 10.13140/RG.2.2.28308.73609
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Essentials of Physics Laboratory Training
ESSENTIALS OF PHYSICS LABORATORY TRAINING
Rajesh B. Khaparde
HBCSE-TIFR, Mumbai, INDIA
(rajesh@hbcse.tifr.res.in)
Introduction to Experimental Physics
Physics is a fundamental science, which provides a picture of how the universe behaves and how
the laws of nature operate under different conditions. In this modern age, there are three divisions
in the approach and tools physicists use to understand nature, namely theoretical, experimental and
the more recently established computational. Thus, fortunately or unfortunately, we have been
forced with three distinct branches, namely, theoretical physics, experimental physics and
computational physics. Each has an important role to play in the development of our understanding
of nature. All the three branches are intertwined in a complex manner and it is difficult to think of
one without the other. The basic approach and tools of experimental physics differs from that of
theoretical and computational physics. Let us try to understand this difference and importance of
experimental physics.
Physicists seek to understand the physical universe in order to predict its behavior under different
conditions. Theoretical physicists develop models and theories, which should always be the
handmaiden of experimental evidence, and the validity of any model or theory is decided by the
way in which its conclusions are supported by experimental evidence. An experimental physicist
starts by observing the behavior of nature and recording the observations and measurements as
data. With this raw data the physicists look for patterns and when the data obey simple
mathematical rules, the patterns are termed as empirical laws. These empirical laws form the basis
of our understanding about the behavior of nature.
We may conjecture that a variety of careful observations about the behavior of nature and the
universe, over a period of time, led man to the discovery of patterns in nature and paved the way for
development of methods of experimental physics, which may be said to be the study of effects
caused by known changes in the system.
Galileo and Fransis Bacon introduced the scientific experimental method, which was further
developed and propagated by Newton, Boyle and others. Scientific method is a procedure through
which observations are made, hypotheses developed, experiments designed and conducted and
conclusions drawn about a clearly defined physical problem. The two crucial assumptions
underlying the scientific method are reproducibility and causality. Through the scientific method,
we try to develop or validate theory, which has to be both self-consistent and consistent with all
known experimental data. This scientific experimental method is an important tool of experimental
physics, which we should develop through the physics laboratory training.
Importance and Role of Laboratory Training
It is no exaggeration to say that physics is the most quantitative of sciences, which is based on
observations, measurements, data collection, analyses and interpretations. Physics aims to explain
physical phenomena of the universe in terms of quantitative relations between various physical
quantities. All the changes in the universe are related to changes in some or other physical
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Essentials of Physics Laboratory Training
quantities. Hence, the teaching and learning of physics is incomplete and inadequate, unless
students gain significant experience in well-planned experimental activities through the laboratory
training. These experimental activities should involve and develop both cognitive and psychomotor
abilities with a proper coordination between them.
One may ask, how the physics laboratory training with a set of simple experiments can be used to
provide an introduction to experimental physics in general? The answer is not so much in the set of
simple experiments themselves but in the attitude, the scientific method and various other cognitive
and psychomotor abilities, which are essential to approach and solve real life experimental
problems. The physics laboratory training offers an opportunity to work with simple experimental
problems and develop the expertise, which we will require later to work on complicated real world
experimental problems.
The role of laboratory training is succinctly expressed in the words of the well-known educationist
and psychologists David Ausubel (1968) “The laboratory gives the students appreciation of the
spirit and method of science…, provides students with some understanding of the nature of
science…, promotes problem solving, analytic and generalization ability”.
In the lecture-laboratory method of instruction, which is the most acceptable and feasible method of
instruction for teaching physics, the laboratory training plays a very important role. It complements
the lecture sessions by providing the student a direct acquaintance with the evidence, processes and
methods of physics. It provides an opportunity for the student to learn to work independently and
creatively and to develop the ability to organize, analyze and interpret experimental observations
and data. The laboratory training helps the student to develop an appreciation for physical
measurements, an understanding of their role and limitations in the generation and substantiation of
physical theories.
The laboratory training provides an opportunity to develop scientific thinking and curiosity as well
as to learn “how to think scientifically”, which may be attributed to the objectives of physics
education. For many students, the laboratory can have a strong motivating influence towards a
career in physics. The laboratory training gives the joy and thrill of doing physics.
Hence training in experimental physics becomes an integral and indispensable part of physics
education. Today virtually at every college and university the world over, laboratory training has
been given a central and important place in physics education.
Objectives of Physics Laboratory Training
The objectives of the physics laboratory training, which are accepted all over the world include the
following.
1) Development of a better and long lasting understanding of facts, concepts, principles and laws
of Physics.
2) Development of procedural understanding/abilities related to designing experiments, planning
measurements/observations and analyzing data.
3) Development of experimental skills for the use, alignment and handling of a wide range of
laboratory instruments and tools.
4) Development of insights and expertise in scientific methods, processes and techniques
commonly used in experimental physics.
5) Fostering different cognitive abilities like hypothesizing, predicting, observing, classifying,
interpreting and inferring.
6) Development of experimental problem solving ability.
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7) Training in the handling of experimental data, making the students aware about the
uncertainties involved in various measurements and development of abilities with respect to the
treatment of data, error analysis and reporting of experimental activities.
8) Development of higher order abilities, like becoming careful and keen observers, ability to
make accurate measurements, proper handling of measured data for objective reasoning and
drawing conclusions and making generalizations.
9) Development of interest, motivation, open-mindedness, creativity, curiosity, scientific
thinking/attitude, self-activity and independent working habits.
It is important to keep in mind all the above objectives while developing the physics
laboratory courses. We should select the ‘contents’ and ‘strategies’ for the physics laboratory
training to achieve most of the above-mentioned objectives. We need to understand that the
emphasis required to be placed on various aspects and abilities will be decided by the level,
method and the content of the courses. This means, the emphasis on a particular aspect will
be different during an introductory course and an advanced course.
Classification of Experimental Activities
In the classification of experimental activities presented here, we have followed the work of Gott
and Duggan (1995). They have identified five types of activities: inquiry, illustration, skills,
observations, and investigations. This classification is mainly based on the roles and major learning
outcomes of the experimental activities. Inquiry type of activities are designed to acquire different
concepts, laws or principles. Illustrative type of activities usually are concerned with understanding
or consolidation of substantive concepts. Skill type of activities are meant for acquiring and
practicing different experimental skills. Observation type of activities are mainly about application
and synthesis of conceptual understanding. Investigations provide the opportunity for students to
synthesize conceptual and procedural understanding and skills to solve an experimental problem.
In the traditional classification of experimental activities, the criterion for classification is the
method of instruction in addition to the role and learning outcomes. In the traditional classification,
I can identify six types, namely, inductive, deductive, verification, skill, investigations and
exploratory. Skill and investigations are common to both the traditional and Gott and Duggan’s
classification. The inductive type is almost the same as the inquiry type and the verification type is
identical with the illustration type. The deductive type can be linked to the observation type,
because both involve theory-laden observations. The exploratory type is not included in Gott and
Duggan’s classification. I feel that this type is important and is distinct from the others. While
presenting our classification of experimental activities, I have added this type to the five types
described by Gott and Duggan.
Thus experimental activities may be classified on the basis of their respective roles, learning
outcomes or their methods of instruction. In the classification described below, we have six broad
types, with each type having a significant role to play in experimental physics. The boundaries
between these types are not watertight; an experiment can clearly include more than one type. For
example, an inquiry type of experiment will not be without skills or data interpretation.
1) Inquiry Type
This type of activity allows students to discover on their own a particular concept, law or principle,
which has not been introduced to them earlier. Activities of this type have to be carefully planned
and set-up to enable all students to arrive at the same end point. Here, the guided discovery
approach may be employed, in which questions may be posed to the students and the necessary
instructions may be given. Students will be required to organize facts, observations and results to
derive meaningful generalizations and principles. The main objective of this type experimental
activity is concept acquisition.
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An example of this type would be a planned and guided experiment in which students are asked to
determine the volume of an irregular body made of a material with unknown density, without any
prior knowledge of Archimedes’ principle.
2) Illustration Type
The objective of this type of activity is to illustrate/verify/consolidate a particular concept, law,
principle, technique or process, which has already been introduced. Students are provided
opportunities to witness events and ‘see’ the concepts in action, so that they relate theory more
closely to reality. This builds students’ confidence and belief in concepts, laws or principles. This
activity may take form of either a demonstration by the teacher or an experiment where students are
given detailed instructions to follow. This type of activities may involve illustration of experimental
techniques and processes or use of instruments also.
A typical experiment of this type, performed either by a teacher or a student is the study (with prior
knowledge of Ohm’s law) of variation of the current passing through a resistor with the applied
voltage for different fixed value resistors.
3) Skill Type
In this type of activity students are given opportunities to acquire and practice psychomotor and
other analytical skills. These activities may involve setting up of apparatus, use of instruments, and
taking measurements or they might require students to learn and practice skills such as recording
observations and data and plotting of graphs. The main objective of this type of activity is acquiring
experimental skills necessary for carrying out experimental work.
One may think of, as an example of this type of experimental activity, a task, where the students are
asked to determine the density of the material of various rectangular or square blocks by measuring
their masses and dimensions.
4) Observation Type
This type of activity has often been described as ‘theory-laden’. Students are asked to observe an
event or a phenomenon and are encouraged to apply previously learned principles to predict,
describe or explain the event. The main objective of the observation type of activity is to develop
an ability to apply conceptual understanding in a new situation or to reinforce major concepts, laws
or principles.
As an example of observation type of activity, one may think a situation where a tiny spherical
metal ball is allowed to fall through a highly viscous liquid and students are encouraged to observe
the motion of the ball with respect to its speed and explain the motion on the basis of previously
learned principles of mechanics.
5) Investigation Type
This type of activity usually offers several alternative ways of reaching a solution of a problem so
that the design is much less controlled than illustrative or inquiry type of activities. In investigative
activities students are supposed to use previously learned knowledge to solve a scientific problem
or to study a phenomenon or an event. These activities provide students an opportunity to achieve a
thorough grasp of procedural understanding, while at the same time they allow students to use and
refine their conceptual understanding. The main objective of investigation type of activity is to
allow students to use or apply conceptual understanding, procedural understanding, cognitive
processes and experimental skills in an integrated manner to solve a problem.
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An experiment where the students are asked to investigate the relation between the electrical
conductivity of the material of a given block and its temperature, without substantial guidance or
procedural instructions, may be considered as an example of investigation type of activity.
6) Exploratory Type
In this type of activity students are given the necessary and possible apparatus and are encouraged
to probe and build up new information through open-ended problems. Exploratory activities
develop both conceptual and procedural understanding, but are different from investigations, in the
sense that they are explorations of different questions and relationships in an unknown situation and
do not have constraints of a definite design. In exploratory activities the end point is not fixed and
hence the design is not at all controlled. In this type, no guidance is given. Instead, students are
given a free hand to choose a particular apparatus, procedures and methods to explore questions
and relationships of interest. The information gathered through exploratory activity can be utilized
by the students to process new information and to find scientific relationships. Exploratory
activities help students to foster creativity, interest and motivation towards the subject. The main
objective of the exploratory activity is to develop an understanding of the methods and processes of
science.
An activity where the students are given, along with other apparatus, a set of pendulum bob like
objects of 1) the same mass and shape but of different volumes, 2) the same volume and shape but
of different mass and 3) the same mass and volume but of different shape, and are expected to
explore on their own the dependence of time period of oscillation of a simple pendulum on
different parameters like volume, mass, shape of the object and the length of the pendulum may be
considered as an example of the exploratory type of activity.
Each type of experimental activity has an important role to play in experimental physics.
Hence the physics laboratory training should have experiments, problems, projects and
demonstrations, which will involve all the six types of experimental activities. This will
develop various abilities and fulfill the objectives of the physics laboratory training.
Procedural Understanding in Physics
For many years, it has been accepted that physics education should be more than just teaching
about ‘things’ that the physicists know and have found out. It should also enable students to ‘think
like physicists’ and understand the ‘nature of physics’. Physics education should include elements
of the procedures used in physics. Let us try to understand what is procedural understanding, which
defines clearly the ‘contents’ of the procedures used in physics.
For defining procedural understanding, we refer to the research work by Richard Gott and Sandra
Duggan, published in the year 1995 in their book “The Investigative Work in Science Curriculum”.
They point out that the content of ‘procedural understanding’ is not well documented, and although
in mathematics the term ‘procedural understanding’ refers basically to recall and use of a set of
rules, in science it has a deeper meaning in its own right. In science, one needs not only to recall
and apply the ‘rules’, but also to relate these rules and associated concepts to objective evidence.
Validity of science essentially rests on objective experimental evidence. It is the collection and
verification of data, which distinguishes procedural knowledge in science from that in mathematics.
Procedural understanding is that understanding, which is often ‘implicit’ and goes behind the
planning and execution of experimental physics in order to systematically generate scientific
knowledge from it. In other words, procedural understanding is that understanding, which enables
an experimentalist to use experimental skills for verifying theory or discovering new knowledge. It
has a critical role in experimental physics. It is an integral part of solving simple as well as complex
experimental problems. Procedural understanding develops an ability to ‘think scientifically’ and is
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a cognitive understanding in its own right, which is essential for the development of our
understanding about the physical universe around us.
Procedural understanding is the understanding of a set of ideas or concepts (like variable
identification, fair test, sample size, variable types, relative scale, range and interval, choice of
instruments), which may be termed as ‘concepts of evidence’, related to the ‘knowing how’ of
science and required to implement science in practice. It forms a link between conceptual
understanding and experimental skills. It is distinct from, yet complimentary to, conceptual
understanding. It is the thinking behind the doing or the decision-making that goes on in
performing experimental activities.
For example, if a student is asked to study the motion of a freely falling body, with respect to its
changing velocity, then all such knowledge as planning of the experiment and decisions to be taken
as to what is to be measured, what the appropriate range of readings will be, with what accuracy,
and at what intervals the measurement will be carried out and how one may derive meaningful
outcome from the measured data constitutes procedural understanding.
Procedural understanding is the understanding of various ‘concepts of evidence’ associated with
design, measurement, data handling and evaluation of the complete task. Let us try to understand
and identify important concepts of evidence.
Concepts of Evidence
Procedural understanding is based on the belief that there is a body of knowledge that underlies an
understanding of scientific evidence. Certain ideas about the collection, analysis, and interpretation
of data have to be understood before we can handle scientific evidence effectively. These ideas
have been called the concepts of evidence. It is these ideas and their application and synthesis that
constitute the ‘thinking behind the doing’. These concepts of evidence have been structured around
the four main stages of experimental work; namely, the design of the experiment, measurement,
data handling and finally but crucially, the evaluation of the complete experiment in terms of the
reliability and validity of the ensuing evidence. By stages, one does not mean, stages in time, since
these stages are often revisited. For instance, at the data handling stage a decision may be made to
take more measurements. The evaluation of the task requires an understanding of all three stages;
design, measurement, and data handling, and this understanding of evaluation is needed as much at
the beginning as at the end of the task.
Gott, Duggan and Roberts have identified more than 50 concepts of evidence that form the
knowledge base of procedural understanding and are required when solving problems in science. It
covers some 19 areas ranging from fundamental ideas of causation and association, through
experimental design, data analysis and interpretation to validity and reliability as overarching
touchstones of evidence ‘quality’. Here we list in Table 1.1 selected important concepts of evidence
associated with the four different stages of experimental work and their definitions.
Table 1.1 Selected concepts of evidence and their definitions
Concepts of evidence
Associated
with the design
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Variable
identification
Definition
Understanding the idea of a variable and identifying
the relevant variables to change (the independent
variable), to measure, or assess if qualitative (the
dependent variable), control variables and irrelevant
variables.
Prepared by Dr. Rajesh B. Khaparde, HBCSE-TIFR, Mumbai, INDIA
Essentials of Physics Laboratory Training
Associated
with the
measurement
Associated
with the data
handling
Associated
with the
evaluation of
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Fair test
Understanding of a fair test which is a systematic
and valid task to draw inference about how the
independent variable affects the dependent variable,
while certain other variables are controlled.
Sample size
Understanding the significance of an appropriate
sample size.
Variable types
Understanding the distinction between categorical,
discrete, continuous and derived variables and how
they link to different graph types.
Understanding the need to choose sensible values
for quantities to be measured.
Relative scale
Range and
Interval
Understanding the need to select a sensible range of
values of the variables within the task so that the
resulting line graph consists of values, which are
spread sufficiently widely and reasonably spaced
out so that the ‘whole’ pattern can be seen.
Choice of
instrument
Understanding the relationship between the choice
of an instrument and the required scale, range of
readings required, and their interval (spread) and
accuracy.
Repeatability
Understanding that the inherent variability in any
physical measurement requires a consideration of
the need for repetition if necessary, to give reliable
data.
Accuracy
Understanding the appropriate degree of accuracy
that is required to provide reliable data, allowing
meaningful interpretation.
Understanding that tables not only present collected
data, but also serve to organize and design the
subsequent data collection and analysis.
Tables
Graph type
Understanding that there is a close link between
graphical representations and the type of variable
they are to represent.
Patterns
Understanding that patterns represent the behavior
of variables and that they can be seen in tables and
graphs.
Multivariate
data
Understanding the nature of multivariate data and
how particular variables within those data can be
held constant to discover the effect of one variable
on another.
Understanding the implications of the measurement
strategy for the reliability of the resulting data; can
the data be believed?
Reliability
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the complete
task
Validity
Understanding the implications of the design for the
validity of the resulting data; an overall view of the
task to check that it can answer the question.
The term variable has been used in Table 1.1 to refer to any observable quantity, which can be
described by different values for example, temperature, length, or time. Variables can be classified
in terms of their roles and functions in the structure of the activity as independent, dependent,
control variables or irrelevant variables. The values for the independent variable are chosen and
manipulated. The value of the dependent variable is then measured for each change in the value of
independent variable. Control variables are those, which must be kept constant while the
independent variable is changed to make the test ‘fair’. One may identify variables, which in a
given situation are irrelevant.
It is important to note that concepts of measurement have to do with the decisions that have to be
taken about measurement rather than to do with the experimental skill of measurement itself.
Concepts associated with data handling include the understanding of the use of a table as a way of
organizing data rather than the construction of a table itself. A further aspect of data handling is the
isolation of the required variable from the multivariate data. The final evaluation stage subsumes all
other concepts of evidence because reliability and validity can only be considered in the context of
the strategy of the whole task. In the above discussion an attempt has been made to restrict the
definition of concepts of evidence to ideas that relate data to reality, which is a crucial distinction
between mathematics and science.
It has been observed that conceptual understanding and experimental skills are the only
aspects recognized in formulating the objectives of laboratory training. What has been by and
large overlooked is the important component of procedural understanding. We believe that
procedural understanding is a kind of cognitive understanding in its own right; it is different
from conceptual understanding and is therefore necessary to incorporate it explicitly in
physics laboratory training. Hence, during the physics laboratory training, we need to
consciously emphasize the development of procedural understanding in addition to other
aspects, namely, conceptual understanding, experimental skills, problem-solving ability and
attitudinal and other affective factors.
Selection of Experiments and Demonstrations
As we know an experiment is a practical inquiry, a repeatable trial to find out what happens, a test
or investigation to verify or falsify a hypothesis, a practical research study for comparison between
two situations under controlled conditions, a set of actions and observations to research the causal
relationship between phenomena. This complex set of actions indicates that an experiment can
include a variety of activities. This makes it essential to carefully select experiments for training in
experimental physics at various levels, keeping in mind the objectives of the training.
It has been observed that although there are some ‘very good’ experiments in the present curricula,
not many experiments are based on fundamental concepts, laws and principles in physics and their
applications. There are many experiments, which are based on the study of basic electronic devices
or circuits, which require very little skills to perform the experiment. Most of these experiments are
of the ‘connect and read’ type, in which students are supposed to make some connections and take
readings by varying either current or voltage, perform routine mathematical calculations and plot
graphs to obtain expected results.
Hence, we need to select experiments such that students get an exposure to a variety of
experimental situations, setups, measurements, measuring instruments, techniques and
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processes. We identified a set of broad guidelines, which may help us in choosing experiments
for a particular course. Of course, all guidelines will not apply to every experiment or
experimental problem; the guidelines that apply to a particular experimental problem are a
subset of the total set of guidelines. In our design and selection of the experimental problems,
we have tried our best to adhere to the guidelines. We do not however claim that we have
been able to do so successfully for every experimental problem.
1) An experiment should be a collection of smaller parts, with each part devoted to a specific task
or goal to accomplish. Each part may have different focus and learning outcome.
2) Experiments should be suitable for and strongly linked to the theory course.
3) Experiments should be chosen keeping in mind the prerequisites and the level of preparation
and training of the students.
4) Experiments are to be carefully chosen so that they are best suited for training and not the
evaluation of different aspects and abilities.
5) As far as possible, experiments should be suitable to be presented as experimental problems.
6) Experiments should directly emphasize the development of all the three important aspects i.e.
conceptual understanding, procedural understanding and experimental skills.
7) Experiments should involve different types of experimental activities. There should be
investigative and exploratory components in the experiments.
8) Experiments should be based on fundamental concepts, laws and principles and their
applications to real life situations and systems.
9) Experiments should involve the combination and application of understanding from different
areas in physics.
10) Experiments should be innovative with respect to the experimental situation, the conceptual
content, experimental design or the techniques used.
11) The experiment should be so designed as to suit the format of presentation and the time
available to students for performing it.
12) The experimental setup and the instruments should be simple, easy to operate, sturdy and work
satisfactorily for a long time giving reliable results with good repeatability. It should not be
confusing and scary to the students. Instead it should look attractive so that students will feel
like working with them.
13) Experiments should encourage students to add some of their own relevant ideas and their
interpretation. Even in traditional experiments, teachers can ‘program in’ unexpected
modifications and surprises.
14) Experiments should engage students in the process of formulating and asking an interesting
question of nature and its behavior.
Carefully designed demonstrations are equally important as experiments and play an important role
in physics education. The demonstrations serve a specific role of illustration of a concept, law,
principle, technique, use of an instrument or an experimental setup. Demonstrations performed by
the teacher or student help to recall and refine the conceptual understanding and develop the
understanding of apparatus, methods and processes involved in experimental physics.
Demonstrations stimulate thinking and develop cognitive abilities like observing, application,
synthesis, interpreting and inferring. They also help students to develop interest, curiosity,
reasoning ability and scientific thinking.
We identified a set of guidelines, which we tried our best to follow. Again all guidelines will not
necessarily apply to every demonstration. We however, do not and cannot claim that each
demonstration has been designed strictly in accordance with these guidelines. The guidelines are as
follows:
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1) Each demonstration should be based either on the key concept of the corresponding
experimental problem or on the use of the tools/measuring instruments/experimental
techniques/experimental setup.
2) Each demonstration may involve one or more types of experimental activities, but will be
basically of illustration and observation type.
3) The demonstration should be a collection of simple activities, questions and related discussions
and should be presented in an interactive mode.
4) Each demonstration should be neat and attractive and have such visual impact that students are
drawn towards it.
5) Each demonstration should be simple to present and should have smooth flow of ideas,
activities and discussions, such that replacement of a particular teacher or demonstrator should
not affect its effectiveness.
6) Each demonstration should stimulate thinking in students and help them develop different
cognitive abilities like keen observation, application, synthesis, interpretation, inferring and
affective abilities like creativity, curiosity, interest, open-mindedness, scientific attitude.
7) The design and development of each demonstration should be preceded with the identification
of its objectives.
8) The experimental setup should be easily duplicable or reproducible and even reparable.
Instructional Strategy
We are of the opinion that the instructional strategy, i.e. the mode in which students work with the
given set of experiments is the most important factor in deciding the effectiveness of training in
experimental physics. We have developed a novel mode of presentation of an experiment and
demonstration, in which, an experiment is presented in the form of an experimental problem with
guiding instructions and a related demonstration is given as an introductory prelude to it. We
developed an innovative instructional strategy for the delivery of the experimental problems and
demonstrations to the students, which may be used for laboratory training for higher secondary and
undergraduate level at various colleges and universities. We describe below various aspects and
details of the instructional strategy.
1) Free Laboratory Atmosphere
We believe that in an effective laboratory training the laboratory atmosphere should be ‘free’, i.e.
where students will be encouraged to carry out self-designed and independent experimental work.
The ‘free’ laboratory atmosphere does not refer to an open ended laboratory or an exploratory type
of experimental activities. Our idea of ‘free’ laboratory atmosphere is that the students are told
about the final outcome of each part of experimental work, but they are given autonomy with
respect to, choice of variables, choice of range of values of variables, range of observations, use of
instruments and experimental techniques (in some cases), method of data handling and analysis etc.
Thus, in this strategy the students are provided a ‘free’ atmosphere with respect to finer procedural
stages, but are still guided with respect to the approach or a possible method of solving the
problem. The students are guided to think and take decisions related to the solution of the each
small experimental stage or part of the problem.
For example, in an experimental problem if the students are asked to study the relation between
incident intensity to the output current of a photodetector, then they may be given a starting
instruction on the possible use of inverse square law, they may be asked to identify the necessary
apparatus with specifications, they may be given some hints for assembling and using the
experimental setup, asked to identify the dependent, independent and control variables, construct a
fair test, identify the sample size, understand the types of the variables involved and thus in short
design the detailed procedure. They may be asked to choose sensible values of variables or
parameters, proper range and interval between different values of these parameters. They may be
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Essentials of Physics Laboratory Training
then asked to record the desired data and analyze the data using tables and graphs to derive
meaningful results.
2) Format of Presentation
We developed an innovative format of presentation of experimental problems based on the
approach followed in the experimental examination of International Physics Olympiad (IPhO). This
format is essentially directed towards inculcating self-reliance and independent thinking on the part
of the students.
We felt that it may not be advisable to present an experimental problem as a single, monolithic unit,
but instead may be presented as a collection of interrelated, successive subsections. In fact, even the
Olympiads, though they are international competitive examinations and not training courses in
experimental physics desist from taking a monolithic approach.
Thus, each experimental problem is presented as a collection of simple smaller experimental stages,
which are interdependent or hierarchical in time. In each stage, the students are given simple tasks.
The tasks are woven in succession so that the whole problem unfolds through them and students
following them are guided stepwise toward the solution, making definite progress through each
step. Thus, students solve the experimental problem in graded stages. Each stage may have a
different focus, may involve a different type of experimental activities and may aim at different
learning outcomes.
The stages and the whole problem are therefore wide and open enough and are far from being
specifically detailed as in programmed learning. In a sense, they are similar to the stages in the
guided discovery method, though at every stage or in the problem as a whole there is not
necessarily a discovery to be made (for the students). Further the guided discovery method has been
used by a large number of people basically for conceptual understanding. In this strategy we use the
‘guided problem solving’ approach and present the experiment as an experimental problem to the
students. Students are individually given a carefully designed handout for each experimental
problem, the corresponding instruction sheet and the answer paper. In this approach, students are
guided through the handout to think of and design their own method, to carry out measurements, to
analyze data and are thus guided and trained to understand and solve experimental problems.
On completion of the demonstration, students are expected to read the student handout of the
problem and understand its objectives. They are then expected to understand the use of different
apparatus and the related warnings or precautions. Students are expected to broadly use the
procedural instructions, design an appropriate method on their own, answer the questions, carryout
the necessary measurement, record the data, carryout the necessary analysis of the recorded data
and derive the required results/inferences.
1) Essentials for Experimental Physics
We feel that there are some important aspects related to measurements, statistical treatment of data,
graphical representation and analysis of data, significant figures and error analysis, which are
essential tools of experimental physics. We have identified some of these aspects as listed in
Appendix A of this book. We feel that, students’ should have a good knowledge and understanding
of these before taking the course in experimental physics. In this strategy, we prepare a detailed
reading material on all these aspects and make it available to the students well in advance. We
expect students to read this material and develop the basic knowledge about all the aspects. During
the initial stages of the laboratory training, a considerable amount of time should be spend on
developing students understanding and confidence with respects to use and regular practice of all
the essentials for experimental physics as mentioned in Appendix A of this book.
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It is important to note the difference between these essentials for experimental physics and the
‘concepts of evidence’, which constitutes procedural understanding. We are of the opinion that all
these tools should be discussed and taught in the classroom mode of instruction with any set of
data. This may be included as a part of the introductory theory course, which will help students as
tools for theoretical as well as experimental physics.
2) Student Handout
In the conventional laboratory training, the teachers carry out an introductory instruction session for
each experiment. Instead, in this strategy students are individually given carefully designed handout
for each experimental problem. Students are expected to work independently with guidance
provided in graded stages through the handout. The description of the experimental problem given
in the handout does not follow ‘cookbook’ format, instead it takes the student away from
mechanically followed instructions to a more self designed and student oriented experimental
activities.
The students are given a brief conceptual introduction to the problem through the handout. They are
also given the necessary description of apparatus and the experimental setup. The necessary
theoretical basis is explained to the students through these handouts and the necessary figures,
schematics, the derivations of formulas and relationships are provided. This theoretical basis is
given in detail since we expect students to understand the required details of theoretical basis of the
experimental problem. The students are then given the procedural instructions. These procedural
instructions are carefully given through the handout with an intension to ‘guide’ students but only
with respect to a general method of handling the problem. The student handout provides 1) brief
introduction to the problem 2) objectives of the problem along with its description 3) apparatus 4)
details of the apparatus and experimental setup 5) useful data and dimensions 6) warning 7) theory
8) procedural instructions and 9) references.
In this strategy, the students are guided through procedural instructions to think of and design their
own method, plan the solution, to carryout the measurement, to analyze the data and thus to solve
the given experimental problem. The students are guided through them and yet given enough
autonomy in making decisions involving various concepts of evidence (for example, variable
identification, sample size, relative scale, range and interval etc.) and other procedural aspects of
experimental work. The student handout for each experimental problem is carefully designed such
that students should be properly guided to develop procedural understanding, experimental skills
and conceptual understanding. Necessary measures have also been taken in designing the handouts
such that students also develop different higher-level cognitive abilities like designing, predicting,
observing, classifying, application, synthesis, interpreting and inferring.
3) Procedural Instructions
Students are given ‘open’ procedural instructions, which guide them to a right start and encourage
them to think on various aspects of experimentation. These instructions guide students’ thinking but
offer a room for independent thinking, designing and planning of actual procedures. These ‘open’
instructions are unlike ‘cookbook’ type of procedural instructions where students are ‘spoon-fed’
directly with actual procedural stages without any scope for independent thinking and designing.
For example the instructions may include, “You may have to use law of Malus; identify the
independent, dependent and control variables; vary the parameter X in convenient and appropriate
steps and study its effect on parameter Y; plot an appropriate graph to determine Z; record the
necessary data to study the inter-dependence of X and Y; determine the value of X graphically”.
The instruction “determine the value of X graphically” informs students that they are expected to
think of and plot an appropriate graph and determine from it the value of the parameter X, but it
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Essentials of Physics Laboratory Training
does not inform them about what the nature and the scale of the graph should be, which parameters
should be plotted, how the parameter X is determined, and so on.
4) The Importance of Questions
The student handout also contains (in procedural instruction section) questions on different aspects
of the experimental problem, including conceptual and procedural understanding, which students
are supposed to answer and report. The questions are carefully planned to develop thinking about
and the understanding of the instructions given through the handout and the answers help students
both conceptually and procedurally. The questions can be asked on different aspects like use of a
graphical method for data representation, interpretation and analysis, choice of scale, choice of axis,
understanding of the sources of errors, need and importance of various finer adjustments and
control of apparatus, application of conceptual understanding to a new situation.
One can use these questions to develop different abilities related to adjustments of experimental
setup, measurements and data analysis. Sometimes the questions are also designed to encourage
students to think on various substantive concepts involved and use them in a new situation to
explain or predict an observation or an effect. These questions serve the purpose of developing the
understanding of procedural understanding, methods and techniques used in experimental science.
The answers enable the teacher to assess students’ abilities and understanding of the subject and
hence to an extent serves as an input for evaluation of a student’s performance.
5) Experimental Arrangement
Students are provided with all the required apparatus and are given a free hand to work in the
laboratory. They are also given some extra apparatus and instruments to choose the most
appropriate instrument for a particular measurement or setup. Students are supposed to assemble
various instruments, connect them and thus make the necessary experimental arrangement on their
own.
6) Role of Instruction Sheet
Along with the student handout for the problems, students are also given an instruction sheet
specifically prepared for that problem. This instruction sheet gives information on the use of
different instruments and apparatus, the adjustment of the apparatus and the necessary safety
instructions, warning and precautions. On a student’s demand, the teacher may provide help about
the use of a new instrument. The teacher may even help students to understand the principle of
working, method of operation, limitations and specifications of different instruments. The users’
manual of various instruments published by the manufacturers may be provided to the students.
7) Availability of Reference Material
The necessary references and books are made available to the students in the laboratory to be used
during the experimental sessions. Also some computers are provided for Internet connectivity and
search. Students may use these sources of information to understand the theoretical basis of the
experimental problems, answer the questions asked in the handout, understand the use and principle
of working of instruments and sometimes even to develop procedural understanding by studying a
similar experimental situation or a demonstration.
8) Laboratory Infrastructure
The laboratory has well thought space, suitable workbenches, desks and chairs, proper water and
electrical outlets. There should be a sufficiently dark room for optics experiments, non-magnetic
furniture for the electricity and magnetism experiments. Also some computers may be provided for
Internet connectivity, data representation and analysis.
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9) Role of the Teacher
Another aspect of the strategy is the minimal intervention by teachers. Students are not offered any
direct advice from the teacher with respect to procedural aspects in solving the experimental
problem instead the teacher plays a role of a silent observer. The teacher provides minimal
guidance to the students. Students are expected and allowed to take their own decisions about
procedures and measurements and hence the teacher may some times coerce students to plan the
procedural details individually on their own. Teachers may help students to understand the use of
instruments or even the theoretical basis of the problem. Thus in this strategy, once the
demonstration is over, during the work on the experimental problem, no direct procedural guidance
is given to the students by the teacher.
In order to have a better teaching-learning ambience, the ratio of the students to teacher in the
laboratory should be 5 to 8.
10) Division of Available Time
Students are given sufficient amount of time, i.e. five to six hours to solve the given experimental
problem. Each experimental problem is carefully designed such that a typical undergraduate student
does not take more than five hours for satisfactorily solving the experimental problem.
Students should initially spend ample time to understand the experiment, relevant theory and
planning of the procedural details by reading the relevant material. Also they should spend good
amount of time on data analysis and reporting of the experimental activities during the laboratory
sessions. Hence, in this strategy during each experimental session, students are expected to spend
about 15 % of the total available time in the beginning on reading, understanding and planning and
about 20 % of the time on data analysis and reporting at the end of each session.
11) Size of the Group of Students
Collaboration is clearly a common feature of most scientific work today. Students should be gently
introduced to the benefits of collaborative nature of scientific research. In case of the laboratory
training collaborative learning helps students to effectively develop different aspects and abilities
related to experimental physics.
The strategy developed by us, is flexible with respect to the size of the group of students. We
observed that the effectiveness of the training is maximum, if the same experimental problem is
given to two students who are expected to work together on the same experimental setup but
independently record, analyze, report and draw inferences from data. Hence, in our case, two
students are given the same experimental problem and are expected to work on the same setup to
solve the given problem. They may use the same set of data but are expected to independently
analyze, interpret and report the data and results.
12) Reporting of Laboratory Work
Students are not observed by a teacher, while they work on experimental problems and hence may
not be evaluated on the basis of direct observations by the teacher. Instead, students’ performance is
only verified or evaluated on the basis of the report of their work produced in the answer paper.
This aspect of the instructional strategy reduces the teachers intervention into the students work and
encourages the students self designed independent experimental work. The students’ answer paper
is treated as the only record of their laboratory work and their solution of the problem. This aspect
of the strategy makes it more useful to be applied for a larger group of students since it requires less
involvement on part of the teacher.
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Students are expected to record and report on every procedural step they adopt during the
experimental work, observations, readings, method, detailed data analysis, final results and
inferences in the answer paper provided to them. Students are allowed to use both CGS and SI units
for reporting their experimental measurements and results. We however suggest that students
should essentially present the final results in SI units.
Comprehensive Evaluation Strategy
In the traditional evaluation strategy, students appear for experimental examinations at the end of
the year. The examination generally consists of one or two experiments to be performed by the
student along with a brief oral test. Most of the time, the examination is based on exactly the same
experiments, which the students had performed earlier throughout the year. The students come
‘prepared’ for these experiments, at times having by-hearted the procedure, observations and even
expected readings and results. There are no clear objective guidelines for grading by teachers.
It may be said that these experimental examinations are a check of ‘how the student has performed
the experiments throughout the year’ and not ‘to what extent he/she has developed conceptual
understanding, experimental skills, procedural and other related abilities’. Since all the students are
not given the same experiment to perform at the examination and the difficulty level of different
experiments varies, the procedure gives undue weight to the ‘luck’ factor. Also this procedure is too
subjective and often biased. The marks, which students obtain in the experimental component, are
often inconsistently high compared to the marks in theory component. Often this leads to only a
small dispersion, that is, the examinations too poorly discriminate among the students. Thus, this
evaluation strategy is non-reliable, non-discriminatory and inadequate from the point of validity. It
is thus unsatisfactory as an achievement test.
We therefore felt an urgent need to develop a comprehensive evaluation strategy in accordance
with the objectives of the physics laboratory training. We believe that for a comprehensive and
sound evaluation strategy, one should use multiple tools and final grading should be only on the
basis of the convergence of the results obtained through such multiple tools. In the traditional
evaluation strategy, only the experimental test is used and there is no separate evaluation of
students’ level of procedural and conceptual understanding.
We believe that there are four important aspects to the ‘objectives of’ or ‘what is taught through’
the physics laboratory training, namely, 1) conceptual understanding 2) procedural understanding
3) experimental skills and 4) experimental problem solving ability. The evaluation strategy should
have suitable tests on all the four aspects with an appropriate weightage for each. The traditional
evaluation strategy uses only the third component. The remaining three components are not
evaluated separately.
We developed the evaluation strategy based on four components or tools of evaluation 1) a test on
conceptual understanding 2) a test on procedural understanding 3) an experimental test to measure
the performance of the students in ‘solving’ an experimental problem and 4) continuous evaluation.
The first two are paper and pencil type tests, which correspond to a single variable each, namely,
the level (or score) of a student’s conceptual understanding and the procedural understanding
respectively. The third is centered around the variable ‘experimental skill’, but is not a single
variable measure; rather it is a composite measure of the experimental skills, problem solving
ability, conceptual understanding and procedural understanding. It is difficult to isolate the
contributions of each of the four variables to this composite measure. The fourth is based on
students’ record of their regular laboratory work throughout the year.
We describe in the following subsections various components/tools of evaluation referred to above.
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1) Test on Conceptual Understanding
We may recall that, conceptual understanding is the understanding of the facts, concepts, laws and
principles. According to our strategy, one should have pen and paper type written tests to
quantitatively measure the students’ performance with respect to this conceptual understanding.
This test should essentially be ‘context linked’, i.e. the questions should have a direct link to or an
application of the conceptual understanding involved in the experimental problems and
demonstrations. The contexts or the situations around which the questions are framed should be
new and novel. This is essential to check the extent students have developed conceptual
understanding through the given course.
This test should mainly have ‘multiple choice’ type questions. It may have ‘match the pairs’ or ‘fill
in the blank’ type questions also. Some questions may involve drawing or completing a figure or a
schematic/ray diagram. The questions should be supported by schematics or figures to clearly
explain the question to the students. It is essential to validate such a test. We have given sample
questions on conceptual understanding (with a context link to the set of experimental problems and
demonstrations) in Appendix B of the book.
Every student should be given a separate copy of the question paper. Students may be asked to
mark their answers on the question paper itself, which is collected after the test and hence no
separate answer paper is needed. Blank papers may be provided to the students for carrying out
rough work. It is important that the students should be given ample time to answer the given set of
questions.
In the marking scheme, marks should be assigned for the correct answer as per the difficulty level
of the question. One may even use negative marking scheme. The marks allotted to each question
and the test may be decided by the number of questions and the difficulty level. The students
should be informed about the marking scheme before the tests.
2) Test on Procedural Understanding
Procedural understanding is the understanding of various concepts of evidence that mediate
between the conceptual understanding and the experimental skills and is necessary to solve the
experimental problems. Usually procedural understanding is evaluated using experimental tests and
observations by the examiner. We felt that the significance of procedural understanding is
subsumed and therefore lost under the rubric of ‘experimental skills’. We feel it is a kind of
cognitive understanding in its own right and hence it should also be tested separately.
According to our strategy, the level of procedural understanding should be measured quantitatively
by the students’ performance in a separately designed test on procedural understanding. Since it is
‘conceptual in nature’, we feel that a pen and paper type written test with appropriately framed
questions based on experimental situations should be used. It is understood that this type of test is
not a replacement of an experimental test in which procedural understanding and various other
abilities are synthesized to solve the given experimental problem.
In this test, questions may be of ‘descriptive’ or ‘essay’ type. One may even have ‘multiple choice’,
‘fill in the blank’, or ‘match the pairs’ type of questions. The questions should be ‘context free’,
i.e., these questions should have no direct bearing on a set of experimental problems and
demonstrations included in the course. It is essential to validate such a test. Some sample questions
on procedural understanding are given in Appendix C of this book.
The test on procedural understanding may have questions on various aspects related to how, why
and what of the design, measurement and data handling like devising a procedure for measuring a
particular parameter, choosing an appropriate instrument, understanding relationships in
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Essentials of Physics Laboratory Training
instruments, determining the range and accuracy required, exercising precautions, controlling
parameters, changing parameters, measures to reduce errors, variable structure, choosing values,
sampling the data, range that is required in the experiment, the intervals between the readings,
reliability and validity of data, data presentation.
Each student should be given a separate copy of the question paper along with an answer paper.
Students should be provided blank papers for necessary rough work. The question paper, the
answer paper and the blank papers should be collected at the end of the allotted time for the test.
Students should be given ample time to answer the given set of questions. Students should be
informed about the marking scheme before the test.
In the marking scheme, on account of variation of contents, length of expected answers and
difficulty levels, it is necessary to give different weightage to different questions. For making the
marking scheme, a detailed model answer for each question should be prepared, analyzed and
accordingly the marks should be allotted to each question. One may not use negative marking in
this case.
3) Experimental Test
According to our strategy, experimental skills and problem solving ability should be quantitatively
measured through separate experimental test. Hence, the third component the comprehensive
evaluation strategy should be an experimental test. It should be noted that the experimental test
gives a composite measure of students’ cognitive (conceptual and procedural) understanding,
experimental skills and problem solving abilities required to effectively solve the given
experimental test. However since all these components of the composite measure are so integrated
with each other that separating their individual effect is hardly possible in such a test.
One should use an identical experimental test to be given to all the students. This will ensure that
all the students are tested on the ‘same ground’ unlike in the case of the traditional evaluation
strategy in which students are given different experiments, which may have different difficulty
levels. The experimental test may be based on some experimental problem, which should be
carefully designed to involve experimental skills and experimental problem solving abilities. A
sample experimental test on ‘efficiency of a light emitting diode’ is presented in this book in
Appendix D.
Every student should be given the set of necessary apparatus, the question paper, the answer paper,
blank papers and graph papers. The question paper should give the necessary details of the
experimental test like the objectives, apparatus, description of the apparatus, useful data and the
statement of the problem.
The students should be asked to report in a systematic manner all the steps they devised and
followed, measurements, data analysis and interpretation. They should report practically every
observation taken and every procedural step followed. This comprehensive reporting will allow
grading the students’ performance after they complete the test based on the report in their answer
papers.
According to our strategy, the students’ performance should be graded entirely through their
comprehensive reports, totally avoiding subjective judgments based on the ‘observations’ and
‘interrogations’ by the examiner. This is an important aspect of our method of evaluation of
students’ performance in an experimental test (based on the method used in the experimental
component of the International Physics Olympiad Examinations). It considerably reduces the
subjectivity of assessment present in the traditional method. Thus, teachers or examiners present in
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Essentials of Physics Laboratory Training
the laboratory should not interact with the students during their tests, unless a student needs to
consult them for technical reasons.
The marking scheme should be carefully and critically designed to evaluate the students’
performance with respect to various aspects and abilities mentioned earlier, which the experimental
test is suppose to evaluate. One should prepare a model answer of the test and then identify various
stages of the solution of the experimental test according to the model answer. One should then
decide the relative weightage for different stages. We feel that students’ reporting is also an
important aspect, which should be evaluated and hence we may reserve some marks for reporting
or presentation of the laboratory work, which may cover proper use and drawing of tables and
diagrams. Marks should be allotted to the experimental skills (reflected from the data),
understanding and application of the necessary theory and concepts, collection, organization and
analysis of data and overall approach towards handling successfully the given experimental
problem.
4) Continuous Evaluation
In our opinion, it is important to keep a check on students work during the regular laboratory
course. Student’s report of each experimental problem, which they ‘solve’ during the course,
should form an important component for the evaluation. Thus the fourth component of the
evaluation strategy is the continuous evaluation based on students work in the laboratory and their
reports. We feel substantial proportion of the total marks should be reserved for this ‘continuous’
evaluation.
In their reports, students should record every procedural step they adopt during the experimental
work, the readings and observations, the method, the detailed data analysis, final results and
inferences. Students should be forced to complete the report of the given experimental problem
before going to the next. The teacher should interact and observe students during the laboratory
course and give quantitative scores for the work. The teacher should continuously correct and give
scores for the report of each experimental problem during the laboratory course. The final
score/marks should be a combination of all the individual scores.
According to our evaluation strategy, one should essentially use all the above-mentioned four
tools of evaluation with an appropriate weightage for each of them. First two tools may be
administered and evaluated centrally. The relative weightage should depend on the level and
objectives of the laboratory course. To give an example, we recommend (for an introductory
course), to have 1) 15% of the total marks for test on conceptual understanding 2) 20% of the
total marks for test on procedural understanding 3) 40% of the total marks for the
experimental test and 4) 25% of the total marks on the continuous evaluation. Thus, we
believe that this evaluation strategy is more comprehensive (tests different aspects), more
objective, more valid and reliable as an achievement test, than the traditional evaluation
strategy.
References
1) Khaparde Rajesh B. and Pradhan H. C. , Training in Experimental Physics Through Problems
and Demonstrations, Penram International Publishing (India) Pvt Ltd. 2007
2) Anderson R. O., The experience of science; A new perspective for laboratory teaching,
Teachers College Press, Columbia University, New York, 1976.
3) Foulds K., Mashiter J. and Gott R., Investigations in science, Blackie, Glasgow, 1990.
4) Gott Richard and Duggan Sandra, Investigative Work in the Science Curriculum, (Developing
Science and Technology Education, B. E. Woolnough, Ed.), Open University Press,
Buckingham, 1995.
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Essentials of Physics Laboratory Training
5) Gott Richard, Duggan Sandra and Roberts Roslyn University of Durham,
http://www.dur.ac.uk/richard.gott/Evidence/cofev.htm
6) Hofstein Avi, Lunetta V. N., The Role of the Laboratory in Science Teaching: Neglected
Aspects of Research, Review of Educational Research, 52, (2), 1982, pp. 201-217.
7) Khaparde Rajesh B. and Pradhan H. C., Physics Laboratory Training: Historical Overview,
Physics Education (India), 18 (3 + 4), 2001-2002, pp. 229-234.
8) Khaparde Rajesh B., Development of Innovative Experimental Problems and Demonstrations in
Physics with Suitable Instructional Strategy for Them and Investigating Their Effectiveness in
Laboratory Training, Ph. D. Thesis, University of Mumbai, Mumbai, India, August 2001.
9) Khaparde Rajesh B. and Pradhan H. C., Procedural Understanding: A Neglected Aspect of
Physics Laboratory Training, Physics Education (India), 19 (2), 2002, pp. 147-154.
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