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' = 2 lambda`
C. `(lambda)/(2) lt lambda' lt lambda`
D. `lambda' = lambda`

Answer

C

Explanation

`E = (hc)/(lambda) - W_(0)` and `2E = (hc)/(lambda) - W_(0)`
`rArr (lambda)/(lambda)` = `(E + W_(0))/( 2E + W_(0)) rArr lambda = lambda ((1 + W_(0)//E)/( 2 + W_(0)//E))`
Since `(( 1 + W_(0)//E))/((2 + W_(0)//E)) gt (1)/(2) so lambda' gt `(lambda)/(2)`