Plane Mirror Lab
Name: __________________________
4th grade PSI
-----------------------------------------------Lab Question
How do plane mirrors reflect objects?
Before You Begin
Explain how you think a mirror reflects an object (where it reflects
the object, how far away the object is, etc.).
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Purpose
During this experiment, you will look at a plane mirror and explore
the specifics of how it reflects objects. Make sure to take as
precise of measurements as you can during this lab and use all of
your group members as you work together to place a pencil in the
right location.
Remember to answer the lab questions during the lab; these are
located in the procedure section and afterwards. Conclusion
questions can be answered after the lab is finished.
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Materials
 small mirror (should fit on a desk)
 two identical unsharpened pencils
 blue tack, clay or putty (to hold the mirror upright and in
place on the desk)
 ruler
 small square piece of cardboard 1” x 1” or 2” x 2”
Procedure
1. Decide on what job each member of your group will have:
Pencil #1 Holder: _______________
Pencil #2 Holder: _______________
Distance Measurer: _______________
Angle Measurer: _______________
2. As a group, use the tack or putty to make your mirror stand up
in the center of your table.
3. Pencil #1 Holder: Place a pencil facing the mirror and hold it in
place.
4. Pencil #2 Holder: Without measuring, place another pencil on
the other side of the mirror where the reflection of pencil #1
appears to be. Ask the Pencil #1 Holder, the Distance
Measurer, and the Angle Measurer how close the second
pencil appears to resemble the reflection from their different
points of view. Make sure pencil #2 matches the reflection in
position and thickness and that everyone agrees the position is
accurate. Hold the pencil there.
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4th Grade PSI
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5. Distance Measurer: Measure and record the distance of pencil
#1 to the mirror. Then measure and record the distance of
pencil #2 to the mirror. Hold the ruler down where you
measured.
Distance from pencil #1 to mirror: __________
Distance from pencil #2 to mirror: __________
6. Angle Measurer: Take the square of cardboard and try to fit it
between the ruler and mirror on both sides.
How does the square of cardboard fit into the angle made by
the mirror and the ruler? Draw a picture of how it fit. (It may
be helpful to draw the picture from above.)
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7. Remove the pencils and ruler from their positions. Place one of
the pencils somewhere else in front of the mirror.
Without actually doing it, predict where you would place
another pencil so that it would line up with the pencil’s
reflection.
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4th Grade PSI
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8. Now take another pencil and place it where you thought it
should go.
Was your prediction right?
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Lab Questions
1. The following represents the first pencil and the mirror as seen
from above.
Draw a big dot where you placed the second pencil.
Draw a line between the two dots for the ruler.
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4th Grade PSI
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Conclusion Questions
1. What do you notice about the distances between the pencil and
the mirror and the pencil reflection and the mirror?
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2. When you had to predict where a pencil would be reflected,
how did you know where it should go?
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3. What is the measure of the angle created from the mirror and
the line connecting the pencil and its reflection? What does this
mean?
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4. Did any of your ideas about how a mirror reflects objects
change from before the lab? If yes, what changed?
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4th Grade PSI
Waves, Light, & Information