Explain the difference:

(a) Point sources and extended sources of light.

(b) Umbra and penumbra.

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Solution

(a)

Point Source of Light Extended Source of light

It is that source of light which forms only the umbra region on the screen of the shadowed object. It is that source of light which forms umbra as well as penumbra region on the screen of the shadowed object.

eg: A pin hole through which sunlight is entering is a point source of light eg: Sun is an extended source of light

(b)

Umbra Penumbra

It is the part of the shadow where all of the light from the source is blocked by the shadowing object. It is the region around the umbra where the light from the source is partially blocked by the shadowing object.

It is formed using an extended source of light. It is formed using point source of light.

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