Trace a Shadow Model

Supplied materials

• Use the supplied fictional observations or model. Paper and pencil are optional; spoken answers are welcome. No equipment or real experiment is needed.

Learn the idea

A shadow is a region receiving less light because something blocks a light path. Draw a pretend lamp on the left, an opaque card in the middle, and a screen on the right. In our simple model, only this lamp supplies light and it shines toward the screen. The card interrupts some paths that would otherwise reach the screen.

Our fictional notes say: without the card, the screen is bright; with the card centered in the path, a dark region appears behind the card on the screen. The dark region is not darkness sent out by the card. It is the part that receives less lamp light. Other light sources would change how dark a real shadow appears.

1. Draw lamp, card, and screen in that order.
2. Draw a path that hits the opaque card and stops there.
3. Mark the dark region behind the card on the screen.
4. Remove the card from your drawing and describe the supplied bright-screen result.

Check your reasoning

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Take it further

Replace the opaque card with a sample whose supplied result is “some light passes through.” The region behind it may receive more light than behind the card; these notes do not tell exactly how bright it will be.

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