Laser Reflection Answer Key
Vocabulary: angle of incidence, angle of reflection, laser, law of reflection, plane mirror,
reflection
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
[Note: The purpose of t
...
Laser Reflection Answer Key
Vocabulary: angle of incidence, angle of reflection, laser, law of reflection, plane mirror,
reflection
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
[Note: The purpose of these questions is to activate prior knowledge and get students thinking.
Students are not expected to know the answers to the Prior Knowledge Questions.]
Imagine you shine a flashlight directly at a mirror, as shown below.
1. Draw an arrow showing the direction
you think the beam of light will most
likely reflect off the mirror.
2. Suppose you tilt the mirror. Draw an
arrow showing the direction the beam
will most likely reflect off the mirror now.
Gizmo Warm-up
Flashlights produce wide beams of light that
have various wavelengths. A laser, on the other
hand, is a narrow beam of light with only one
wavelength. All the waves in a laser beam are
parallel to one another. As a result, lasers are
ideal for studying reflection, or how waves
bounce off a surface.
Using the Laser Reflection Gizmo, you can
adjust the position of a laser beam and mirror to
study how light behaves when it is reflected.
1. Drag the Angle slider back and forth. Describe what happens to the reflected laser beam:
Sample answer: As the angle of the mirror changes, the angle of the reflected beam also
changes.
2. Drag the laser up and down. Describe what happens to the reflected laser beam:
Sample answer: The reflected beam moves up and down, but its angle does not change.
Activity A:
Reflection from a
plane mirror
Get the Gizmo ready:
Set the Laser location to 0 cm.
Set the Angle to 25 degrees.
Make sure Plane mirror is selected.
Introduction: A plane mirror is a perfectly flat, smooth surface. In this activity, you will study
how plane mirrors reflect light.
Question: How does the angle of a mirror determine the angle of the reflected light?
1. Observe: Turn on Show normal. The normal is the dotted line perpendicular to the mirror.
The angle of incidence (θi) is the angle between the incoming laser beam and the normal.
The angle of reflection (θr) is the angle between the reflected laser beam and the normal.
Move the Angle slider back and forth. What do you notice about the sizes of θi and θr?
Sample answer: They increase and decrease with the angle of the reflected beam, but they
remain equal in size to each other.
2. Measure: Set the Angle to 40 degrees and turn on Show protractor. Each marking on the
protractor represents 10 degrees
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