Light of wavelength `lambda` strikes a photo - sensitive surface and electrons are ejected with kinetic energy is to be increased to `2 E` , the wavelength must be changed to `lambda'` where

Options

A. `lambda'=lambda/2`
B. `lambda'=2lambda`
C. `lambda' lt lambda`
D. `lambda/2 lt lambda' lt lambda`

Answer

d

Explanation

`E_(k)=(hc)/lambda-phi_(0)` and `2E_(k)=(hc)/(lambda')-phi_(0)`. These relations will be satisfied is `lambda'gtlambda//2` and `lambda'ltlambda`