Question

a spherical mirror and spherical lens both have focal length of -10cm. they both are likely to be?​

Answer 1

Explanation:

By convention, the focal length of a concave mirror and a concave lens are taken as negative. Hence, both the spherical mirror and the thin spherical lens are concave in nature.

Answer 2

The mirror and lens is CONCAVE MIRROR and CONCAVE LENS respectively.

• We know that, for spherical mirrors, concave mirrors (i.e. converging mirrors) have negative sign of focal length.

• Similarly , for lens , concave lens (i.e diverging lens) have negative sign of focal length and power.

This is mainly due to SIGN CONVENTION followed in Ray Optics Coordinate Geometry.

• In both these type of mirrors and lens, the direction of focal length is opposite to the direction of ray, hence considered as negative.

$\star$ Hope It Helps