Question

Light of frequency $ v $ falls on material of threshold frequency $ v_{0} $ . Maximum kinetic energy of emitted electron is proportional to :

• A. $ V-{{V}_{0}} $
• B. $ V $
• C. $ \sqrt{V-{{V}_{0}}} $
• D. $ {{V}_{0}} $

Answer 1

Answer: (A)

When light falls on a metallic surface, ejection of photoelectron results. In this process, conservation of energy hold.
Thus, from law of conservation of energy,
energy imparted by the photon = maximum kinetic energy of the emitted electron + work function of the metal
or $ hv = ( KE)_{ max} + \phi $
but $ \phi = hv_0 , \, v_0 $ being threshold frequency.
or $ ( KE)_{ max }= hv - hv_0 $
or $ ( KE)_{ max} \propto v - v_0 $