The image of an object, formed by a plano-convex lens at a distance of 8 m behind the lens, is real is one-third the size of the object. The wavelength of light inside the lens is 2/3 times the wavelength in free space. The radius of the curved surface of the lens is

Options

A. 1m
B. 2m
C. 3m
D. 43

Answer

C

Explanation

`mu=lambda_(a)/lambda_(m)=3/2`
`implies1/f=(mu-1)/R=1/(2R)`
`implies 1/f=1/v-1/uimplies 1/8-1/(-24)=1/(2R)`
`(3+1)/24=1/(2R)implies=3cm`