Q.

A photoemissive substance is illuminated with a radiation of wavelength λi so that it releases electrons with de-Broglie wavelength λe. The longest wavelength of radiation that can emit photoelectron is λ0. Expression for de-Broglie wavelength is given by (m = mass of the electron, h = Planck's constant and c = speed of light)         [2025]

1 λe=hλ02mc  
2 λe=hλi2mc  
3 λe=h2mc(1λi-1λ0)  
4 λe=h2mc(1λi-1λ0)  

Ans.

(4)