Question

The maximum velocity of electrons emitted from a metal surface of negligible work function is'V' when frequency of light falling on it is f. What will be the maximum velocity when the incident light frequency is made 4f?

Answer 1

Maximum kinectic energy of the emitted photo electron is :

K_​max = 1/2mV² = hf ----- (1)

where m is the mass of the electron
V is maximum velocity of the emitted photo electron
f is the frequency of the incident photon.

when incident frequency becomes 4f, kinectic energy of the photo electron is given by

1/2mV²_final = h×4f ----(2)

divide equation (1) and (2),we get

V²_final /V² = 4/1
V_final = 2V