THIRD YEAR PHYSICS LABS
640-393 and 640-394
SEMESTER ONE, 2009
GENERAL NOTES:
This is a collection of documents introducing you to the 3rd year lab experience. I will be
communicating by email to your university accounts throughout the semester, so please get in
the habit of checking them every so often.
Enclosed you will find a form that needs to be returned, either electronically or in person
wherein you will choose which experiments you would like to do. To this end, a description of
the experiments is included. Also included are important dates, a description of how the
system works, and a really useful guide to writing 3rd year lab reports. You should read all
attached material carefully and inform me of your preferences as soon as possible; first come,
first served. Feel free to contact me with any queries or comments. The surest way to contact
me is by email:
part3@physics.unimelb.edu.au
We look forward to seeing you all in the course of the semester. Enjoy your time in the labs!
Best regards,
Stephen Marshall & Roger Rassool
Part III Lab coordinators
SCHOOL OF PHYSICS
Part III Laboratories - 2009
IMPORTANT DATES
Tuesday 10th March: The laboratory coordinator should have been informed of your
preferences for experiments by the end of this day at the very latest.
Thursday 12th March: at 9 am: INTRODUCTORY SESSION
A short introductory session will be held in the Part III John Rouse Reading Room (ground
floor, Nuclear Building, directly beneath the Part II laboratory). This session will be most
useful to students who have not done any work in the third year laboratories before. It will be
short, so be punctual.
Tuesday 17th March at 9 am: COMMENCEMENT OF PART III LABS
Students participating in experiments starting from this date must bring a bound A4
notebook for this and every other laboratory session.
Most experiments are located on the ground floor of the Nuclear building, astronomy Labs will
be conducted on level 2. Research experience laboratories will operate both at University and
at the Synchrotron, these will also require work outside of the normal laboratory timetable to
accommodate available beamtime.
A book of around 70 pages should suffice for any given experiment, but most experiments will
not require this much space. Depending on your lab allocation, you may or may not receive your
books back in time to write the next lab up in them, so it is wise to assume that a new book will
be required for each experiment.
It is intended that a final version of the laboratory session allocations will be posted on the
part III webpage (www.ph.unimelb.edu.au/~part3) by Wednesday Wednesday 11th March.
Intermediate versions will be posted as soon as preferences are received.
GENERAL ARRANGEMENTS
Part 3 Office
The Part 3 (3rd year) Laboratory Office is located in Room N210 in the Nuclear Physics
Building, where you will find the Part 3 laboratory coordinator, Stephen Marshall. However, I
am not always in my office! The best and preferred way to contact me is by email.
All announcements and general communications relating to laboratory work will be made via
email to the student lists, the part 3 website, and the LMS.
Notices may also appear on the notice boards in the corridor outside the John Rouse Reading
Room and in the relevant laboratories. The coordinator's office hours will appear on the office
door during semester, but you can make an appointment to see me at any time (contact details
below).
Part 3 Lab website
All the relevant information that you need will be posted on the part III website:
http://www.ph.unimelb.edu.au/~part3/ , which is being migrated to
http://thirdyearlabs.ph.unimelb.edu.au as soon as possible (a quick link will take you to the
correct one).
Here you will find this mailout, timetables, and copies of the lab notes. It is a really good idea
to print out copies of the notes before you enter the lab. Note that the compilation date
appears on the front- be careful to use the most recent version of the notes. Copies of all this
information will be moved to the LMS, however the website will always be more up to date.
Laboratory Session Times
Laboratory work is done in the mornings from Tuesday to Thursday. The laboratory hours are
from 9.00 am to 1.00 pm, and you are expected to be in attendance for the full 4 hours. Your
timetable may list Tuesday’s session as running from 8-12, this is due to a timetabling issue,
Laboratories will still run from 9-1, however the last hour of Tuesdays session may be used to
attend physics colloquia (rather than being in attendance at the labs). Students will work in
pairs (occasionally threes) over the course of 2 weeks to complete a single experiment, and will
complete a total of three experiments over an 8 week laboratory timetable (with 2 weeks stand
down). Students experiencing clashes between their lab work and lectures/tutorials for other
subjects should contact the lab coordinator first, and then negotiate with demonstrators.
Research Experience Laboratories will require work outside of these hours to accommodate
availability at the synchrotron.
The Reading Room
The John Rouse Reading Room is open from 9:00 am to 5:00 pm Monday to Friday throughout
the semesters, and is a dedicated space in which third year physics students can work during
the day, whether related to laboratory work or other studies. However, laboratory related
work has priority during lab times.
Borrowing reference texts
Most of the reference texts can be found in the Baillieu library, but there are some texts
available for loan from the part 3 office, and reading room. It is worthwhile having a look at the
references, especially if you feel that you don’t quite understand some aspect of the
experiment.
Laboratory Reports
Experimental work and data are to be recorded in your laboratory notebook as your
experiment proceeds, so there is no need to spend a great amount of time writing up. You
should, however, allocate some time after each lab session to update your log. You are not
expected to generate a lengthy report written after completion; a short conclusion is
sufficient. We do expect a competently maintained, legible and concise experimental notebook
reflecting the actual work done. You are strongly advised to consult your demonstrators at an
early stage of each experiment for both advice and criticism on what is required for the report
and other aspects of your work, for each different experiment.
Handing in Laboratory Reports
Laboratory notebooks are to be placed in the slots provided outside the corridor on Level 2
leading to the Part II Laboratory by 5 pm on the Friday of the final week of the experiment or
laboratory unit. Note this allows one day after your laboratory unit is completed until the lab
book is to be handed in. Penalties may be imposed on your laboratory mark for late books unless
either a medical certificate is produced, or prior alternate arrangements have been made with
the part 3 lab coordinator (Stephen). Medical certificates etc. should be handed in directly to
the part 3 lab coordinator. Notebooks should never be handed directly to demonstrators – we
need to keep proper records of their receipt, marks and return to student. Books will generally
be marked and returned within 2 weeks, but for practical reasons, this may not always be
possible.
Assessment
Your written log book is worth 2/3 of your mark for each experiment. The other 1/3 is based on
your performance in the lab-teamwork, experimental skills, and attitude. If you are unsure what
we are looking for, ask your demonstrators. They will be the ones assessing you. There is a
marking scheme descriptor posted on the website which covers the approach demonstrators will
take in assessing each component of your log book.
The Journal report
Each student will be expected to write up one of the experiments as a formal report, called the
Journal report. It will be expected to be of a professional standard, both in presentation and
content. It will be worth a set 15% of the final lab mark. Further details will be supplied at an
introductory meeting around the middle of semester.
SELECTION OF EXPERIMENTS
Students intending to undertake Third Year Physics Laboratory will have enrolled in one or
more of 640-393 or 640-394, though students choosing to major in physics and/or intending to
apply for entry to the 4th year honours/masters program normally do a full 12 weeks (both units
393 and 394).
Please read the following notes carefully and indicate (preferably by email) the experiments to
which you would prefer to be allocated, for 640-393 or 640-394. You should not exceed 6
weeks in any given semester. You should indicate your first preferences (at least 6 weeks worth
in total) and at least two second preferences. You should also nominate if you are interested in
being part of the research experience program, which will be offered as a substitute for third
experiment of high performing students.
You will note that in Part III you typically spend quite long periods on individual experiments,
and consequently will only be able to undertake a limited selection of the many experiments
available. You should also note that while many of the Part III lecture courses cover material
that is also covered in some of the experiments, no Part III lectures are prerequisites for or in
any way coordinated with Part III laboratory work. You may choose some experiments to
complement your course work and extend your breadth of experience, and others to go deeper
into areas of particular interest to you.
For these reasons you may wish to consult with Part III lecturers or the part 3 lab coordinator
before making your preferences. All students must have their laboratory selections for
semester I made before 10th March, 2008. Every effort will be made to accommodate them,
however please note that preferences received after the due date may have selections further
restricted due to timetable limitations.
Stephen Marshall
Part III Laboratory coordinator
Roger Rassool
Part III Academic coordinator
Room N210
Nuclear Building, School of Physics
University of Melbourne,
Room 409
email: roger@physics.unimelb.edu.au
Phone 03 8344 5100
email: part3@physics.unimelb.edu.au
Phone 03 8344 5077
SCHOOL OF PHYSICS
Part III Laboratories
OUTLINE OF EXPERIMENTS
NUCLEAR/PARTICLE PHYSICS
The overall purpose of the laboratory is to acquaint students with the procedures of nuclear
physics. These are now in widespread use in all branches of the physical sciences. In the
laboratory students use radiation detectors to observe charged particles and gamma rays, and
nuclear reactions are analysed.
Mossbauer Effect (2 weeks)
The Mossbauer Effect is the resonant absorption and emission of gamma rays by nuclei. The
problem with such absorption/emission involves the recoil of the nucleus and, although the
recoil energy is tiny, it is enough to prevent such absorption from taking place. By fixing the
nucleus in position in a crystal allows that recoil to be absorbed by the crystal, allowing for
incredibly accurate measurements of the gamma ray energies. This is the most accurate
experiment in the Part III labs with measurements possible to 1 part in 109. Exploiting this
effect then allows for very detailed elemental analysis in applied physics. The experiment
involves setting up a Mossbauer system and using it to identify 57Fe, the nucleus for this case,
in various molecules, and the physics thereof.
KEK, Analysis of B Meson Decay (2 weeks)
One of the fundamental questions in particle physics is why the universe is dominated by
matter and not by anti-matter. CP (Charge-Parity) violation is one way of explaining this
asymmetry. This phenomenon was first observed in the neutral Kaon (KL) system in 1964. The
extent of the CP violation, however, was insufficient to explain the asymmetry. Thus the search
continued.
In this lab the students will be looking at data from the Belle experiment, which was designed
to measure CP violation in the B meson system where the effect is expected to be larger. This
data was part of the data set that was used to discover CP violation in B meson system by
studying the decay times of the B0 and
mesons. Utilising a 3-D event display to view and
interpret both the Belle detector and the decay of the B meson, the students will be required
to reconstruct the B meson decay chain contained in the data.
Muon Detection and Lifetime Measurement (2 weeks)
In this experiment a multi-layer system of absorber and scintillator panels is used to detect
muons and measure their lifetime. A convenient source of muons is the decay of pions
generated in the upper atmosphere by incident cosmic ray protons. Fast electronics and
accurate timing is used to detect the passage of muons through horizontal scintillator panels
connected by light guides to photomultiplier tubes. Some of these may stop in the apparatus,
detected by their non-passage through lower scintillator detector panels and side veto panels.
These decay via muons decaying to (electron + neutrino + antineutrino), with a lifetime of about
2 microseconds, whereupon the emitted electron may be detected. Students build up the
detector system with appropriate timing and logic connecting the various individual detectors in
a fashion similar to that of the vastly larger and more complicated detector systems used in
modern high energy accelerators.
SEMICONDUCTOR PHYSICS
Scanning Probe Microscopy (2 weeks)
The techniques used in Scanning Probe Microscopy (SPM) allow for the highest resolution 3D
measurements of surface properties of materials to date. SPM incorporates Atomic Force
Microscopy (AFM), which is sensitive to inter-atomic Van der Waals forces as well as
electromagnetic forces, and Magnetic Force Microscopy (MFM), in which a tip is magnetized in
order to render it sensitive to magnetic forces.
In this experiment students will examine the surface topology and magnetic properties of a
hard disk as well as other materials using both AFM and MFM modes of the SMEENA scanning
probe microscope. Students will gain an understanding of the forces involved in AFM, an
understanding of electron tunneling, and how SPM allows for the imaging of materials at high
resolution in atmosphere and at room temperature.
Deep Level Transient Spectroscopy (2 weeks)
Analysing semiconductors (e.g. Silicon wafers) using Deep Level Transient Spectroscopy (DLTS)
reveals vital information about the nature and effect of defects present in the semiconductor.
DLTS is one of the few techniques that probes the traps in the band-gap introduced by ion
implantation of dopants.
The experiment involves analyzing a Silicon wafer which has been implanted with light ions, and
characterizing the defects arising from implantation. The sample is cooled with liquid nitrogen,
a metal contact is deposited to form a Schottky diode, and the capacitance measured under a
variety of voltage pulses and temperatures.
Superconducting Quantum Interference Devices (2 weeks)
Using SQUIDs, as they are known, is one of the most sensitive ways of measuring a magnetic
field currently available. For this reason, they are widely used in medical applications such as
Magnetic Resonance Imaging. The heart of the SQUID is an interface of two superconductors
called a Josephson junction, through which Cooper pairs of electrons tunnel according to
quantum mechanics. This experiment will introduce the SQUID and explore its basic properties.
ATOMIC-OPTICAL & MAGNETISM
The experiments in the Atomic - Optical and Magnetism Laboratory centre about the study of
electron energy levels in atoms and molecules. In the Atomic - Optical laboratory students
observe the spectra arising from various transitions using precision optical systems and analyze
their results by directly applying their knowledge of Quantum Mechanics.
Zeeman Effect (2 weeks)
The Zeeman Effect involves the splitting of electronic energy levels by the application of a
magnetic field. A precision Fabry-Perot etalon is used to observe the low level spectral line
splitting due to the Zeeman effect in mercury. The Fabry-Perot etalon is a sensitive instrument
capable of precise measurements of visible light wavelengths (1 in 5 x 107 accuracy). Students
apply the fundamental principles of quantised angular momenta in an attempt to develop an
understanding of the observed phenomena.
Hyperfine Structure (2 weeks)
The Bohr model of atomic structure predicts, quite accurately, the electronic energy levels of
Hydrogen atoms. Larger atoms with more electrons have more complex spectra, with energy
levels dependent on electron-electron, spin-orbit and relativistic effects. These effects create
the ‘fine structure’ of atomic spectra. Atomic energy levels may also be affected by extremely
weak interactions between the orbiting electrons and the nuclear magnetic dipole, and electric
quadrupole, moments. These effects produce extremely fine splitting of spectral lines. This
hyperfine structure is observed and measured by students using a Czerny-Turner
spectrometer. Students perform an extensive quantum mechanical analysis of their data based
on a model of the interactions involved.
Nuclear Magnetic Resonance (2 weeks)
Nuclei placed in an external magnetic field will have their atomic energy levels split into 2s+1
sub-levels (where s is the nuclear spin). Resonant absorption and emission of radio-frequency
photons will induce transitions between the sub-levels. The phenomenon of NMR is studied and
observed in a variety of materials, using a RF generator and detector interfaced with a fast
Digital Storage Oscilloscope. The form of signal detected is affected by a number of secondary
effects, including spin-lattice interactions, spin-spin interactions, thermal effects, and chemical
effects. These effects are observed and explained by the students. Students develop skills in
the use of a modern fast Digital Storage Oscilloscope interfaced with a laboratory computer.
Optical Pumping (2 weeks)
Optical pumping involves shining light at a collection of atoms in order to raise some of their
electrons from the ground state into an excited state. Such a process is at the heart of lasers
and slow atom optics. In this case, you will be exciting gaseous Rubidium using a discharge lamp
pulsing at radio frequency. By using a magnetic field and a polariser, you will be 'pumping' the
electrons from the ground state into a particular excited sublevel, and comparing the
absorption characteristics of the gas with those predicted by quantum mechanics.
ASTROPHYSICS
Observational Astronomy (2 weeks)
This includes a set of four exercises and short projects aimed at familiarizing students with
some of the techniques of practical astronomy. It does not assume any previous background in
astronomy. The topics covered will include:
(i) Charge Coupled Device (CCD) analysis of a galactic star cluster. This will enable a
Hertzsprung-Russell diagram to be established yielding information on stellar temperatures,
luminosities and masses.
(ii) Measurement of the Milky Way rotation curve. Using a small radio telescope to observe the
velocity of neutral hydrogen in the Milky Way, a picture of how our galaxy rotates can be
obtained.
(iii) Clusters of Galaxies photographed with the 48’’ Schmidt telescope are examined to
estimate the value of the Hubble constant and thus the age of the Universe.
(iv) Uncatalogued Asteroids captured on high quality photographic plates are analysed to
determine the location and thickness of the asteroid belt as well as an estimate of the total
number of asteroids present in the belt.
Computational Astrophysics (2 weeks)
This experiment involves astrophysical simulation exercises based on a laboratory computer.
Students use Fortran or C to write computer programs to perform numerical simulations of
processes of astrophysical interest. Students can develop algorithms for the simulation of
binary stars, atmospheric braking for spacecraft, and the passage of a black hole through our
solar system.
RESEARCH EXPERIENCE
Please note that if you choose any of these labs, it may possibly involve work outside of normal
lab hours. You will be provided with plenty of notice so that you can make appropriate
arrangements. Before undertaking any of the field work, you will have to undertake and
complete the necessary OH&S Safety training.
RE-1 Linear Accelerator, Booster and Storage Ring:
The linear accelerator (or linac) uses a series of RF cavities, operating at a frequency of 3 GHz,
to accelerate the electron beam to an energy of 100 MeV, over a distance of around 15 metres.
Due to the nature of this acceleration, the beam must be separated into discrete packets, or
'bunches'. These bunches are then directed into the booster where further acceleration of the
beam to 3GeV is achieved by a simultaneous ramping up of the magnet strength and cavity
fields. Finally, the electrons are extracted from the booster and delivered to the storage ring,
216 metres in circumference and comprised of 14 nearly identical sectors. Each sector consists
of a straight section and an arc, with the arcs containing 2 dipole 'bending' magnets each. Each
dipole magnet is a potential source of synchrotron light and most straight sections can also host
an insertion device.
A range of research experience based experiments will be offered in collaboration with the
Aust. Synchrotron Accelerator Physics Group . These will typically consist of spending the first
week at university attending mini seminars with accelerator physicists from the synchrotron. In
the second week of the laboratory, you will have an opportunity to be based at the synchrotron.
RE-2 Advanced X-ray Diffraction (2 weeks)
The scattering of x-rays is a powerful method of determining the arrangement of atoms within
a crystal. Interpretation of the angles and intensities of these scattered beams can lead to
the production of a three-dimensional picture of the density of electrons within the crystal.
From this electron density, the mean positions of the atoms in the crystal can be determined,
as well as their chemical bonds, their disorder and various other information.
Since very many materials can form crystals — such as salts, metals, minerals, semiconductors,
as well as various inorganic, organic and biological molecules — X-ray crystallography has been
fundamental in the development of many scientific fields.
A range of research experience based experiments will be offered in collaboration with the
beam line scientists at the Australian Synchrotron. In the second week of the laboratory, you
will have an opportunity to be based at the synchrotron.
RE-3 Radio Telescope (2 weeks)
The radio telescope on top of the Redmond Barry Building will be used by students to measure
Doppler shift in various stellar objects. Radio spectra have some distinct advantages over
optical spectra in determining redshift. Firstly visible light is far more prone to dust extinction
than radio signals, and due to the amount of dust within our galaxy, this can pose problems for
optical measurements.
Data from the telescope will be collected remotely, and students will gain experience
programming the telescope to run unattended. Other observations may be undertaken, and a
determination of the speed of galactic rotation, as a function of distance from the galactic
center can be made.
Please note that safety regulations are to be observed in the laboratories at
all times.
SCHOOL OF PHYSICS
Part III Laboratories
REQUEST FOR LABORATORY ALLOCATION, 2008
Please email your preferences to part3@physics.unimelb.edu.au before Tuesday 10th
March, 2009. If you don’t have email access, you can complete this form in hardcopy and snailmail it to Stephen Marshall, School of Physics. University of Melbourne, or hand it in to my
office, level 2 Nuclear Building.
Students must complete 6 weeks worth of laboratory work (usually 3 experiments) in any given
semester.
Students may not undertake more than 6 weeks of experiments in any single semester.
Please indicate the experiments you prefer to be enrolled in by placing a number 1 next to
them. Also, place a number 2 next to at least two additional experiments which will be used if
any of your first choices are unavailable. Also indicate if you are interested in being selected
for the research experience based laboratories.
SURNAME:
OTHER NAMES:
STUDENT NUMBER:
CONTACT TELEPHONE:
Email address:
I am providing my preferences for
640-393 only
640-394 only
Both 640-393 and 640-394
LABORATORY
PREFs
EXPERIMENTS
Nuclear and Particle Physics
Mossbauer Effect
Computer analysis of KEK data
Muon detection and lifetime measurement
Semiconductor Physics
Scanning Probe Microscopy
DLTS
SQUIDs
Atomic-Optical and Magnetism
The Zeeman Effect
Hyperfine spectra in Hg
Nuclear Magnetic Resonance
Optical Pumping
Astrophysics
Observational Astronomy
Computational Astrophysics
Research Experience (tick one or all you would be interested in)
RE-1 Accelerator Physics
RE-2 Advanced XRD
RE-3 Radio Telescope
You may note any special requests, e.g., exceptionally loaded parts of semesters which you
would like kept free of prac.
Stephen Marshall
Part III Laboratory coordinator
Room N210, School of Physics,
University of Melbourne,
Parkville, VIC 3052.
email part3@physics.unimelb.edu.au
Phone 03 8344 5077
THIRD YEAR LOG-STYLE REPORTS
AND HOW TO WRITE THEM
In third year we ask you to provide a log-style report at the end of the fortnight. This is a
hybrid term, implying an approach which is both chronological and rigorous with respect to the
physics (careful analysis including errors, clear explanations of motivations and
understandings). Those of you who have done the second year physics laboratory subject
should already be familiar with the basic requirements – in third year we expect to see “the
same, but more”.
It might be useful for you to think a little about the way our expectations of you have changed
since you started doing physics in first year. Demonstrators in first year, though they are
trying to teach you some physics, are also trying to make sure that you understand the very
basics of report writing – what an aim should be like, the fact that your method should be what
you do as you do it, the importance of labeling axes on graphs… In second year we assume
that you know these sorts of things, and concentrate on emphasizing the importance of rigour
in scientific method – typically this comes through as an obsession with error analysis and
method, with “doing it properly”. By the time you reach third year, demonstrators expect that
you have already had two years of training in the basic requirements of a scientific report
(structure, rigour), and feel free to concentrate on different things – specifically your
understanding of the (often quite high level) physics you’re doing!
Having said that, your demonstrators realize that third year marks can be important, and that
students are keen to gain a good understanding of each subject’s requirements. It’s very
important that you understand the criteria on which you will be assessed. It’s also important
that you know why your assessment takes the form it does. This handout attempts to explain
some of these matters. You should feel free to consult your demonstrators and the laboratory
coordinator about them at any time.
Log Books and Reports
A log is a detailed and honest account of what you do as you do it. It involves taking note of
instrument settings, file names, sources of uncertainty, problems with the equipment (and how
these were solved or why they weren’t), descriptions of both things you did wrong and things
you did right. This is the way you show us that you are applying the scientific method to the
problem you are investigating.
A report is more like a story – the story of how your understanding has grown. It’s full of
sentences (or dot points!) explaining what’s going on, why you’re doing things, how your results
connect up with the theoretical understanding you have. This is the part that teaches your
reader all about the experiment. It also explains the significance of your results, and their
limitations.
One of the reasons we ask you for this hybrid-style report is because your lab report has to
fulfill two aims. One is to act as a true scientific log. Anyone should be able to take your log
book into the lab and replicate your experiment exactly without needing to refer to other
materials. You should be able to take your log book back into the lab 3 years later and repeat
the experiment, find your old results (i.e. have a record of your file names and what each file
was) and check that the new results and the old ones are the same (to within error!).
The second aim is pedagogical – we need to find out how much you understand. For this reason,
and because being able to convey results clearly is an important skill in science, your report
needs to have some basic structure to it:
(i)
(ii)
(iii)
(iv)
(v)
There has to be some background theory – we need to know you understand the
context within which the experiment is being carried out, and what makes it
interesting or significant. (Why do I care about finding this number?)
There has to be an aim – we need to know that you understand what you’re trying to
achieve.
There has to be a thorough method (i.e. show us you knew what you were doing and
why at each step). Since this is a log-style report, we actually expect to see one large
Method/Results/Analysis section. Often you will start with some simple
measurement, do some basic analysis, and then go back and take more (or different)
measurements. The latter measurements will only be possible because of the
extended understanding the first measurements/analysis provided. You need to show
us that you understand both the significance of the first measurements and the
motivation for taking the new ones.
There has to be some theory in the body of the report. Normally the background
theory you provided at the start will only be an overview, which you will need to
extend as you proceed. Extensions to the theory (derivations etc) should be
integrated into your Results/Analysis. They will be part of your explanation of your
experimental results.
There has to be a conclusion. This should summarise your results (with uncertainties,
and comparisons to expected values if necessary), answer the aim, and perhaps include
a brief statement of the limitations of your results. We have to know you understand
what you found out. What is not required is an extended discussion – that should all
be part of your analysis. You conclusion, like your aim, should be concise.
A good way to make sure that your report stays clear and thorough is to keep a very specific
reader in mind – someone stupid, lazy and mean. If you can get someone like that to
understand what you’re doing and believe that you did it in a scientific way, you’re bound to get
a good mark!
Some tactics for achieving both of these aims:
a) Firstly, it’s a good idea to start with the background theory, even before the aim. That
way you can define the important terms, give an overview of what’s being investigated,
and then make your statement of the aim of the prac very concise and specific.
b) An excellent tactic is to write only on the facing page of the book – this gives you the
left hand side of the book to use for rough notes and sketches, or “back of the envelope”
calculations.
c) Don’t be afraid of spending time writing in class – you will only find out if you really
understand the experiment when you try to write it down, and it’s much better to do that
while your demonstrators are there to help out when you get stuck.
d) You will probably need to spend half an hour or so after each prac session updating your
log book. This is common practice in any research lab, and is one of the skills you need to
develop.
e) Keep things neat on the way through – i.e. put results straight into tables rather than
keeping scraps of paper with wandering columns and random numbers written on them.
That way if you run out of time at least your results are clear, and you have something to
refer to. It also makes keeping track of your uncertainties – either as a single figure at
the top of the column, or as an extra column – easy.
f) It’s a good idea to number the pages of your log as you go. That way if you answer a
question on the second day, do some more work and then realize your answer wasn’t quite
right it’s very easy to go back, cross it out, and refer your reader forward to another
page.
g) Lots of students like to get their calculations “right” before they commit them to
“proper paper” – this is a waste of time for two reasons. One is that whatever happens
you’re going to have to include a sample calculation in your report, so if your “practice”
calculation is correct you’ll just have to transcribe it. The other is that if you spend all
day struggling with a calculation but then just present a single clean number in the
report, your reader will have no understanding of why you (for example) didn’t get all of
the analysis finished. The phrase “this is wrong because” is just as important as “this is
because” – in some ways it’s more important, because it shows us how you coped with
problems, whether you were critically evaluating your results on the way through etc.
Even an admission like “Apparently I can’t use a calculator – comparison with my partner
showed a discrepancy between our results. I’ve done these calculations again on the next
page…” is evidence of the fact that you’re checking that your results can be replicated.
h) Make your diagrams nice and big – at least a third of a page. That makes them easier for
you to draw and easier for your reader to understand.
i) Take the extra time in Excel to add proper titles to your graphs, axes etc when you first
create them. You will typically be producing multiple graphs, and it’s very, very easy to
forget which is which.
These are by no means the only tactics you can employ, and you will no doubt develop your
own way of working over the course of your weeks in the lab. The best way to avoid having
to be up all night the night before you hand your reports in, though, is simply to do things
properly while you’re in the lab. Although it’s important to be able to get a rough idea of
how things work, the real key to good science is pedantry – doing things carefully in the first
place, and then double-checking afterwards. There are quick and dirty ways of doing things,
(and if you’re running low on time you may find that your demonstrators tell you about them
so that you can get some sort of a result before the end of the prac,) but in general you are
in the third year labs to show us that you can do science. This means that the answer to the
question “do I have to (repeat these measurements, do errors for this…)?” is almost always
“yes”.
A Note On Lab Performance
You receive a mark out of 10 for your performance in the lab. This makes up one third (1/3)
of the mark you receive for each experiment. It is often the result of discussion between
your demonstrators, so that one bad day doesn’t affect your mark too much in a two week
lab. It involves an assessment of how you perform while actually in the laboratory, and
includes things like:
a)
b)
c)
d)
were you in regular attendance?
did you work safely?
did you approach the experiment methodically, and with attention to detail?
did you work effectively with your partner? (Did you sit back and let them do the
work? Did you ignore them or monopolise the equipment so that they were unable to
work?)
e) did you show an understanding of experimental technique?
f) were you able to identify problems as they arose, and perhaps suggest solutions?
g) were you able to work independently, attempting the solution to problems before coming
to your demonstrator? (NB this does NOT mean you should avoid asking questions! It
means that your demonstrators are not there to do the prac for you – they will point you
in the right direction, then expect you to make an attempt yourself.)
A Final Note
The catchword of the third year labs is independence. In these labs you will have the time
to really explore some serious physics, and though your demonstrators will be there to act
as guides, they will expect you to be working independently of them most of the time. They
will show you how things work, point out the danger areas, and refer to you to books where
you can find out the details, but they won’t be standing behind you, watching over your
shoulder. They expect you to be mature enough experimentalists to be able to cope with
some of the problems you encounter on your own. They also expect you to be mature enough
to come and ask them for help when you’re stuck – if you tell them you’re OK (even though
you’re struggling) they’re quite likely to take you at your word. Having said that, they are all
there because they love physics and enjoy working with you – they are one of the best
resources available to you, so make use of them and enjoy the labs as much as you can!