PHYSICS
LAB: R AY BO X/PLA NE M IR RO R S
NAME _____________________________
DATE ___________________ PERIOD ____
LAB PARTNERS: __________, ____________, _____________, ___________, ___________
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1. Bounce a single ray of light off a plane mirror at an angle incidence of 0°. Rotate the mirror by
20°, 40°, 60° and 80°, and note the amount that the reflected ray rotates.
a. Summarize the observed behavior in a single sentence, without using specific numbers of
degrees:
b. How do you use a plane mirror to make a light ray bend 90°?
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2. Set up two mirrors at right angles. Bounce a ray of light so that it reflects from both mirrors. Try
this a number of times with a variety of incident angles.
a. What relationship exists between the original incident ray and the final reflected ray?
b. Place two small mirrors at right angles on top of a larger mirror. This is known as a "corner
reflector." Observe, and see if you can figure out how this would behave.
A bicycle reflector is composed of many miniature corner reflectors. Examine the reflector
available in class.
Explain why a “corner” mirror would be used for a bicycle reflector
A corner reflector was left on the moon by Apollo astronauts, allowing us to bounce laser light from it. By
timing the travel of the light from earth to moon and back, and then multiplying half this time by the speed of
light, we can accurately determine the distance between the earth and the moon at any time.
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3. Examine one of the periscopes available in class (either the large ones or the smaller ones). Try
reversing the top mirror while you continue to look in the same direction in the bottom mirror.
Briefly describe what happens.
Use two, three or four light rays, and two of the plane mirrors to simulate a normal periscope. Note
the orientation of the light rays that reflect from the bottom mirror. Reverse the orientation of the
bottom mirror, and note effect on the orientation of the light rays. (NOTE: Try letting the top ray
pass through a colored filter before it hits the first mirror...that will enable you to easily identify it
after the final reflection...compare this for the two mirror positions.)
Draw two diagrams that show the two situations discussed above. USE A RULER OR STRAIGHTEDGE!
NORMAL
BOTTOM MIRROR REVERSED
4. Measure the mirror angle on the kaleidoscope which has been taken apart (located on the front
desk...please leave it there!).
Mirror angle: __________degrees
Based on your earlier lab experience where you counted images in mirrors at various angles, how
many TOTAL views (images PLUS object) would you expect to see in the kaleidoscope? Show a
brief calculation based on the relationship you discovered previously.
Count the TOTAL number of views, or "pieces of pie," that you actually see in the kaleidoscope.
One of these is the object, and the others are images.
TOTAL number of views, or "pieces of pie," seen: ______
Number of IMAGES formed: ______
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5. Look very carefully at the reflection of some object in the thick plane mirror at your lab station.
Place the object fairly close to the mirror, and look very ca re full y at the image. You should be
able to see "ghost" images (fainter images, not quite on top of the main image). Count the ghost
images you can see, and then answer the questions below.
a) There seem to be _____ ghost image(s) on one side of the main image, and _____ ghost
image(s) on the other.
b) Light can reflect from both the front and back surfaces of the mirror. (Keep in mind that you
can actually see your reflection in a plain piece of glass like a window.) It can also reflect back into
the mirror from the inside of the front surface. Continue the ray diagram below to show the first
fo ur light rays that reflect back into the air from the mirror. Label the four rays as follows:
Ray corresponding to the main image: label M
Rays corresponding to ghost images reflected from the front of the mirror: label F
Rays corresponding to ghost images reflected from the back of the mirror: label B
Air
Glass