A convex lens has mean focal length of 20 cm. The dispersive power of the material of the lens is 0.02. The longitudinal chromatic aberration for an object at infinity is

Options

A. `10^(3)`
B. 0.8
C. 0.4
D. 0.2

Answer

C

Explanation

(c ) The separation between the images formed by extreme wavelengths of visible range is called the longitudinal chromatic Is given by,
`f_(1)-f_(2)=omegaxxf`
Where, `omega` is dispersive power
Given, `pmega=0.02,f=20cm`
`because f_(1)-f_(2)=0.02xx20=0.40`