Question

A concave mirror of focal length f. in vacuum is placed in a medium of refractive index 2. Its focal length in the medium is
(a) $\frac{f}{2}$
(b) f
(c) 2f
(d) 4f

Answer 1

(b) F

focal length doesnt change when its is in different mediums

Answer 2

The correct option is (b) "f".

Explanation:

It is given that,

A concave mirror of focal length f. The refractive index of the medium is 2. We need to find the focal length in the medium. We know that focal length is equal to the distance from the pole of the mirror to the focus. It is independent of the refractive index of the medium. Hence, the focal length will remains the same i.e. f.

Hence, the correct option is "f".

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Focal length

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