Activities

1. Start with the mask and just one of the light sources. This illuminates part of the screen. Let's say you wanted to illuminate a larger part of the screen. Could you do this by moving the light source? If so, do you move the light source toward the screen or away from the screen? Could you, instead, illuminate more of the screen by moving the mask? If so, do you move the mask toward the source or away from the source? Could you, instead, illuminate more of the screen by moving the screen? If so, do you move the screen toward the mask and the source or away from the mask and source?
2. Before you turn on the second source, predict the color that will be produced in a region that is illuminated by both sources simultaneously. Turn on the second source (so both the red source and the blue source emit light), and check your prediction.
3. Using two sources and the mask, determine the conditions under which the sources light up distinct (non-overlapping) regions on the screen, and when they light up overlapping regions of the screen.
4. Now use just one source and an object, which casts a shadow on the screen. Let's say you wanted the shadow to cover a larger part of the screen. Could you do this by moving the light source? If so, do you move the light source toward the screen or away from the screen? Could you, instead, produce a larger shadow on the screen by moving the mask? If so, do you move the mask toward the source or away from the source? Could you, instead, produce a larger shadow on the screen by moving the screen? If so, do you move the screen toward the mask and the source or away from the mask and source?
5. How do your answers to activity 1 compare to your answers to activity 4? Explain what the connection is between the two activitoes.