IIT/FIELD MUSEUM – High School Transformation Project
Lesson: Mirror, mirror
Conceptual Physics, Hewitt
Unit IV Sound and Light, Chapter 29.1-29.4
Guiding question
How does light travel from an object to your eyes if the light is reflected by a mirror?
Context of Lesson
This lesson is an introduction to ray diagrams, the behavior of mirrors, and a chance for students to gain practice
graphing and drawing diagrams. Students will also have to use empirical data to confirm or deny a hypothesis.
Main Goals/ Objectives
By the end of this lesson, students will be able to:



formulate ideas about how reflected light travels to your eyes
apply the concept of reflection to a mirror system with multiple reflections
draw a ray diagram to represent the path of light approaching and reflecting from a mirror
Nature of Science: Integrated Theme
2. Distinguish observations from inferences, explain that inferences should be based on observations, and explain
that the development of scientific knowledge involves both observations and inferences so scientific knowledge is
partially inferential.
6. Explain that scientific knowledge should be based on empirical data.
Scientific Inquiry: Integrated Theme
1. Explain that scientific investigations all begin with a question, but do not necessarily test a hypothesis.
3. Explain that inquiry procedures are guided by the question asked.
6. Explain that research conclusions must be consistent with the data collected.
7. Explain that scientific data are not the same as scientific evidence.
General Alignment to Standards
State Goals
 11.A.4b Conduct controlled experiments or simulations to test hypotheses.
 11.A.4f Using available technology, report, display, and defend to an audience conclusions
drawn from investigations.
PSAE Goals
STANDARD 11A – SCIENTIFIC INQUIRY
 11.11.01 Understand and follow procedures relating to scientific investigations, including
understanding the design and procedures used to test a hypothesis, organizing and analyzing data
accurately and precisely, and producing and interpreting data tables.
 11.11.02 Distinguish among the following: observing, drawing a conclusion based on observation,
forming a hypothesis, conducting an experiment, organizing data, comparing data.
STANDARD 12C – MATTER AND ENERGY
 12.11.70 Understand the reflection, refraction, diffraction, interference,
and frame of reference properties of waves.
Bell ringer:
If an object is real, is the image formed in the mirror real or virtual? Are reflections of reflections of reflections
backwards or forwards?
Name:____________________________________________per:_____________date:______________
Mirror, Mirror - Model Lesson activity
Part 1: reflections
Required Equipment/Supplies
2 small plane mirrors
Supports for the mirrors
2 single-hole rubber stoppers
2 pencils
2 sheets of paper
Transparent tape
Discussion
Have you ever held a mirror in front of you and another mirror in back of you in order to see the back of your
head? Did what you saw surprise you? If the image of a coin is reflected by a mirror, do the letters appear
forwards or backwards? What about reflections in 2 mirrors?
Procedure
Step 1: Place the pencils in the rubber stoppers. Set
one plane mirror upright in the middle of a sheet of
paper, as shown in Figure A. Stand one pencil
vertically in front of the mirror. Hold your eye
steady at the height of the mirror. Locate the image
of the pencil formed by the mirror. Place the
second pencil where the image of the first appears
to be. If you have located the image correctly, the
image of the first pencil and the second pencil itself
will remain “together” as you move your head from
side to side.
1. How does the distance from the first pencil to the
mirror compare with the distance of the mirror to
the image?
Fig. B
Step 2: On the sheet of paper, draw the path you
think the light takes from the first pencil to your eye
as you observe the image. Draw a dotted line to
where the image appears to be located as seen by
the observing eye.
Now, Hinge two mirrors together with transparent tape. Set the mirrors upright and at right angles to each other
in the middle of a second sheet of paper. Use the clay to hold the mirrors in place. Place a pencil in its stopper
between the mirrors, as in Figure B.
2. How many images do you see? Why?
Step 3: On the paper, show where the images are located. Draw the paths you think the light takes as it goes
from the pencil to your eye.
Now, decrease the angle between the two mirrors.
3. What happens to the number of images you get when you decrease the angle between the two mirrors?
Part 2: Multiple Reflections
Required Equipment/Supplies
2 plane mirrors, 4 in. × 5 in. viewing object
transparent tape, protractor
clay, toy kaleidoscope (optional)
Procedure
Step 1: Hinge the two mirrors together with
transparent tape to allow them to open at various
angles. Use clay and a protractor to hold the two
mirrors at an angle of 72°. Place the object to be
observed inside the angled mirrors. Count the
number of images resulting from this system and
record in Data Table A.
Step 2: Reduce the angle of the mirrors by 5
degrees at a time, and count the number of images
at each angle. Record your findings in Data Table A.
Step 3: Study and observe the operation of a toy
kaleidoscope, if one is available.
Data Table A
Angle
Number of
images
72o
67o
62o
57o
52o
47o
42o
37o
32o
27o
Analysis questions
1. Explain the reason for the multiple images you have observed.
2. What effect does the angle between the mirrors have on the number of images?
Extension
3. Using the information you have gained, draw and explain the construction and operation of a toy
kaleidoscope.
Name:___________________Key________________________per:_____________date:______________
Model lesson activity: Mirror, Mirror
Required Equipment/Supplies
2 small plane mirrors
Supports for the mirrors
2 single-hole rubber stoppers
2 pencils
2 sheets of paper
Transparent tape
Part 1: reflections
Discussion
If an object is real, is the image formed in the mirror real or virtual? Are reflections of reflections of reflections
backwards or forwards?
Procedure
Step 1: Place the pencils in the rubber stoppers. Set
one plane mirror upright in the middle of a sheet of
paper, as shown in Figure A. Stand one pencil
vertically in front of the mirror. Hold your eye
steady at the height of the mirror. Locate the image
of the pencil formed by the mirror. Place the
second pencil where the image of the first appears
to be. If you have located the image correctly, the
image of the first pencil and the second pencil itself
will remain “together” as you move your head from
side to side.
1. How does the distance from the first pencil to the
mirror compare with the distance of the mirror to
the image?
The distances are the same.
Fig. B
Step 2: On the sheet of paper, draw the path you
think the light takes from the first pencil to your eye
as you observe the image. Draw a dotted line to
where the image appears to be located as seen by
the observing eye.
Now, hinge two mirrors together with transparent tape. Set the mirrors upright and at right angles to each other
in the middle of a second sheet of paper. Place a pencil in its stopper between the mirrors, as in Figure B.
2. How many images do you see?
There are three images: one in each mirror and one in the “crack.”
Step 3: On the paper, show where the images are located. Draw the paths you think the light takes as it goes
from the pencil to your eye.
Now, decrease the angle between the two mirrors.
3. What happens to the number of images you get when you decrease the angle between the two mirrors?
The number of images increases.
Day 2: Multiple Reflections
Required Equipment/Supplies
2 plane mirrors, 4 in. × 5 in. viewing object
transparent tape, protractor
clay, toy kaleidoscope (optional)
Discussion
Have you ever held a mirror in front of you and another mirror in back of you in order to see the back of your
head? Did what you saw surprise you? If the image of a coin is reflected by a mirror, do the letters appear
forwards or backwards? What about reflections in 2 mirrors?
Procedure
Step 1: Hinge the two mirrors together with
transparent tape to allow them to open at various
angles. Use clay and a protractor to hold the two
mirrors at an angle of 72°. Place the object to be
observed inside the angled mirrors. Count the
number of images resulting from this system and
record in Data Table A.
Step 2: Reduce the angle of the mirrors by 5
degrees at a time, and count the number of images
at each angle. Record your findings in Data Table A.
Step 3: Study and observe the operation of a toy
kaleidoscope, if one is available.
Data Table A
Angle
Number of
images
72o
67o
62o
57o
52o
47o
42o
37o
32o
27o
Analysis questions
1. Explain the reason for the multiple images you have observed.
Many images of an object can be seen in a two-mirror system due to multiple reflections, as the light bounces
back and is reflected by another mirror.
2. What effect does the angle between the mirrors have on the number of images?
The number of images increases as the angle decreases.
(Extension) 3. Using the information you have gained, explain the construction and operation of a toy
kaleidoscope.
A simple kaleidoscope contains three mirrors with their reflecting surfaces facing one another 60° apart along
the length of a tube. Colored chips in a compartment are placed between the mirrors. The result is an infinite
pattern made of six symmetrical images.