Define refractive index of a transparent medium. What is its unit? Which has a higher refractive index glass or water? The radius of curvature of a spherical mirror is 20 cm. What is its focal length

Explanation

The ratio of the speed of light in the free space (c) to the speed of light in given medium (V) is called its refractive index.
`n = C/V
It has no unit, glass has more refractive index than water.
Radius of curvature, R = 20cm
Radius of curvature of a spherical mirror = 2 x Focal length (f)
`R = 2t`
`t. = R/2 = 20/2 = 10 cm`
Hence, the focal length of the given spherical mirror is 10 cm.