When monochromatic red light is used instead of blue light in a convex lens, its focal length will :

Options

A. Does not depend on colour of light
B. increase the squeeze of the lens
C. Decrease
D. Remain same

Answer

B

Explanation

Focal length of a lens is given by
`(1)/(f) = (mu-1) ((1)/(R_(1)) - (1)/(R_(2)))`
`(1)/(f) propmu prop(1)/(lambda) implies f prop lambda`
`lambda_(R) gt lambda_(B) implies f_(R) gt f_(B)`
Focal length will increase