# Ray Diagram Practice Worksheet _ Three Light Sources

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```					Chapter 10 – Sources and Properties of Light
Science 8

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LAB – Watching Light Travel
Name: ___________________ Date: ____________________ Block: ____________

Introduction:

The diagrams below show light beams traveling from light sources toward an opaque
object.

Using light and a solid object, you will explore shadow formation and create diagrams that
show the shadow and its parts. It is important that you think of light as traveling in rays.
Light does not really travel in rays, but thinking this way helps us understand some of the
properties of light.

Purpose:

To determine what property of light allows shadows to form.

Materials:

• rubber stopper
• 1 ray box (you will have to share for the part that requires 2 ray boxes)
• ruler
• pencil
Chapter 10 – Sources and Properties of Light
Science 8

Procedure:

Part A – One light source
1. Put a rubber stopper (large side down) on this paper in the space below.
2. Place a ray box 5 cm away from the stopper, and aim a wide light ray toward the
stopper. Make sure that the ray travels on both sides of the stopper.
3. Using a pencil, draw a line around the stopper.
4. Use a ruler to draw the outside edges of the shadow behind the stopper and also to
draw the outside edges of the light from the ray box.
5. Remove the stopper and turn off the light source.
stopper, and umbra on your diagram.

Diagram for Part A:
Chapter 10 – Sources and Properties of Light
Science 8

Part B – Two light sources

1. Set up the stopper again as in Part A, but aim light rays
from two ray boxes toward the stopper (both about 5 cm
away from the stopper). See figure 2.
2. Use a pencil and ruler to outline the stopper, the umbra
and the penumbra. Also draw the outside edges of the
light from the ray boxes.
3. Remove the stopper and turn off the light source.
the umbra than for the penumbra. Also label the two light
sources, the stopper, the umbra, and the penumbra           Figure 2

Diagram for Part B:
Chapter 10 – Sources and Properties of Light
Science 8

Analysis Questions:

1. What can you conclude about the property of light that causes shadows to form?

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2. Explain how the property of light illustrated in this lab also prevents us from seeing
around corners.

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3. Compare figure 1 with your ray diagram from part A. Does a wide light ray from a single
ray box act like light from a small source or from a large source?

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4. Where would the light source need to be placed so that there would be no shadow at
all?

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Conclusion:

In this lab, it was discovered how ________________ are created. When one light source
was used, only the ____________ part of a shadow was formed. When two light sources
were used, both the ____________ and the _______________ parts of a shadow were
formed. Since shadows were formed in both cases, it can be concluded that light
_____________________________________.

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