Question

What are the different types of shadows? Write a few differences between umbra and penumbra.

Accepted Answer

Shadow is a place or a region where the source light gets restricted by the opaque substance not to enter. This region is nothing but a shadow. Its size, sharpness, and shape may vary by various factors. We have two different types of shadows based on the light source. They are Point Light Source and Nonpoint Light Source.

Point Light Source- If the lower light source is pointed to a single area and casts on a shuttle, then the shadow is known as the umbra.

Nonpoint Light Source-If the light source doesn't have a specific point and is extended to spread, based on the size of the light source, we can define and observe the brightness of shadows. These can be determined in three ways. They are Umbra, Penumbra, Antumbra.

Umbra is a complete shadow and penumbra is a partial shadow. Umbra decreases with an increase in the distance from the sun. Penumbra increases with an increase in the distance from the sun. Umbra means ‘’shadow’’ while ‘’penumbra’’ means to hang on the shadow or almost a shadow. Also, penumbra was coined by Johannes Kepler whereas the coining of ‘’umbra’’ is not attributed to anyone in particular. Umbra is the dark part while penumbra is the lighter part. ‘’Umbra’’ is similarly defined as shade while penumbra means partial shade. The penumbra is situated at the perimeters while the umbra is at the center, directly behind the object. Correspondingly penumbra is synonyms with marginal. During a total lunar eclipse, the earth’s inner shadow or umbra falls directly in the moon and at mid-eclipse, the moon may look blood red as it is entirely covered with shadow. When a partial lunar eclipse occurs, the umbra merely covers a part of the moon. The outer shadow of the earth falls on the moon during a penumbral lunar eclipse. During an eclipse, the umbra gets smaller as the distance from the sun increases. On the contrary, the penumbra gets bigger as the distance from the sun increases.

What are the different types of shadows? Write a few differences between umbra and penumbra.

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