Gizmos: Penumbra Effect (Question and Answers)

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Vocabulary: eclipse, penumbra, point source, umbra Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Try this experiment: Shine a flashlight (or a desk lamp) on your hand so that it casts... a shadow on a sheet of white paper. Hold your hand about 15–30 cm (6–12 inches) above the paper. 1. Look at the edges of the shadow. Are they sharp or fuzzy? They are fuzzy 2. Move your hand up and down. How does this affect the fuzziness of the shadow? The closer it gets the more fuzzy 3. Why do you think the shadow has fuzzy edges? The light sources are obstructed and by objects and appear fuzzy Gizmo Warm-up The fuzzy edge of a shadow is the penumbra, a region where light is only partially blocked. The Penumbra Effect Gizmo™ demonstrates why penumbras form. To begin, check that the Number of lights is 1. Click the light to turn it on. The gray block casts a shadow. 1. The light is a point source, which means that all of the light rays emanate from a single point. Does the resulting shadow have sharp or fuzzy edges? It has a clear defined shadow [Show More]

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