Chapter 10 – Sources and Properties of Light Science 8 ________________________________________________________________________ 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. 6. Shade the area of your diagram where the shadow was. Label 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. 4. Shade the umbra and penumbra. Use darker shading for the umbra than for the penumbra. Also label the two light sources, the stopper, the umbra, and the penumbra Figure 2 on your diagram. 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? _____________________________________________________________________ _____________________________________________________________________ 2. Explain how the property of light illustrated in this lab also prevents us from seeing around corners. ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ 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? ______________________________________________________________________ 4. Where would the light source need to be placed so that there would be no shadow at all? ______________________________________________________________________ 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 _____________________________________.