4 page lab.
Seed Question: Make a small circle with your pointer finger and thumb. Look at the shadow of your hand on the wall from the incandescent bulb. Make sure the light goes through the hole in your hand. What is the pattern of light you see on the wall? Now pull your hand farther away, how does the pattern change?
Exploration: Investigating shadows and images.
Part 1 set-up: Use a showcase bulb in your light box frame for a light source. Your mask is one side of a file folder with a small square hole. Use a sheet of thin white paper for the screen. All distances are approximate: you don’t need to measure them with a meter stick. Make a sketch (about 1/2 of your page tall) of this set-up for Part 1:
You can put the screen right up against the mask if you want and look at the pattern of light from behind the screen.
Q1. What pattern of light do you get on the screen?
Q2. What happens to the pattern when you rotate the mask sideways?
Q3. Is the shape of the pattern you see based on the shape of the hole or the shape of the filament?
Draw four rays of light on the diagram above: two from the top and two from the bottom of the filament that graze the edges of the hole and hit the screen. Does the shadow pattern you observed make sense in terms of these rays?
Page 2
Part 2 set-up:Make another sketch (about 1/2 of your page tall).
Now answer these questions:
Q1. What pattern of light do you get on the screen?
Q2. What happens to the pattern when you rotate the mask sideways?
Q3. Run your finger down the glass wall of the bulb between the filament and the mask. What do you see?
Q4. Is the shape of the pattern you see based on the shape of the hole or the shape of the filament?
Draw two rays of light on the diagram above: one from the top and one from the bottom of the filament that graze the edges of the hole and hit the screen. Can you see how the small hole in this configuration acts like a “ray sorter”? What is meant by the term “ray sorter?”
Page 3
Global wrap-up:
Q1. Under what circumstances do you get an “image” of the filament? (Talk about relative distances and sizes.)
Q2. Under what circumstances do you get a “shadow” of the mask?
Page 4
Big Idea:
Discussion: ?