Question

Ultraviolet radiations of different frequencies new1 new2 are incident on two photosensitive materials having work functions W1 W2 respectively. (W1W2) The kinetic energy of emitted electrons is same in both the cases. Which one of the two radiations will be of higher frequency?

Answer 1

Kinetic energy of the emitted photo electron is:

K.E = h$\nu$- w
$\nu$= incident frequency of light
w= work function of metal

For two different frequencies and work function :-
K.E₁ = h$\nu$_​1-w₁-----(1)
K.E₂ = h$\nu$₂-w₂ ----(2)
as K.E₁=K.E₂
if we know the relation between the work function of the two materials,we can calculate which frequency is higher.