The kinetic energy of an electron is E when the incident wavelength is `lamda` To increase ti KE of the electron to 2E, the incident wavelength must be

Options

A. `2lambda`
B. `lambda//2`
C. `(hc lambda)/(E lambda + hc)`
D. `(hc lambda)/(2E lambda + h c)`

Answer

3

Explanation

`(hc)/(lambda)=w+ErArrw=(hc)/(lambda)-E`
Also, `w=(hc)/(lambda^(1))-2E`
Now, `(hc)/(lambda)-E=(hc)/(lambda^(1))-2E`
`lambda^(1)=(lambdahc)/(hc+lambdaE).`