Chapter 4: Problem 44

Define umbra and penumbra.

Short Answer

Expert verified

Answer: Umbra and penumbra are both parts of a shadow created by an object blocking light from a source. The umbra is the darkest part of the shadow, where the light source is completely blocked by the object and appears as a dark area with sharp edges. On the other hand, penumbra is the outer part of the shadow, surrounding the umbra, where some light from the source reaches the observer, but not all of it, resulting in a partially shaded area with less defined edges.

Step by step solution

Introduce the concept of light and shadows

Light travels in a straight line from the source, such as the sun or a lamp. When light encounters an object, it creates a shadow behind that object. Shadows are areas where light is blocked by the object.

Define umbra

The umbra is the darkest part of a shadow, where the light source is completely blocked by the object. In this region, no direct light from the source reaches the observer. It appears as a dark area with sharp edges. You can think of the umbra as the "full" shadow.

Define penumbra

The penumbra is the outer part of the shadow, surrounding the umbra. In the penumbra, some light from the source reaches the observer, but not all of it. This means that the penumbra is a partially shaded area where the light appears to be partially blocked by the object. The penumbra has less defined edges and appears softer than the umbra.

Explain the relationship between umbra and penumbra

Both umbra and penumbra are part of a shadow created by an object blocking light from a source. The umbra is the darker, fully shaded area, while the penumbra is the lighter, partially shaded area surrounding the umbra. The size of the umbra and penumbra depends on the size of the object and its distance from the light source and the observer.

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Define umbra and penumbra.

Short Answer

Step by step solution

Introduce the concept of light and shadows

Define umbra

Define penumbra

Explain the relationship between umbra and penumbra

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