A parallel beam of white light falls on a convex lens. Images of blue, yellow and red light are formed on other side of the lens at a distance of `0.20m, 0.205m` and `0.214m` respectively. The dispersive power of the material of the lens will be

Options

A. `619//1000`
B. `9//200`
C. `14//205`
D. `5//214`

Answer

C

Explanation

For a lens `f_(1)-f_(2)=omegaf_(y)`
`impliesomega=(f_(r)-f_(v))/(f_(y))=(0.214-0.200)/(0.205)=(14)/(205)`.