Question

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. Define Focal length and Lens.

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Answer 1

Answer:

the distance between the centre of a lens or curved mirror and its focus it is focal length and lens is a piece of glass or other transparent material with curved sides for concentrating or dispersing light rays, used singly (as in a magnifying glass) or with other lenses (as in a telescope).

Answer 2

Answer:

Hii Mate,

Focal length

Focal length is the distance between the optical center and Principal focus of the lens.

Lens

Lens is a transparent medium, bounded by two surface, of which at least one is spherical.