Question

Two radiations of photons energies 1 eV and 2.5 eV, successively illuminate a photosensitive metallic surface of work function 0.5 eV. The ratio of the maximum speeds of the emitted electrons is ______.

Options

• 1 : 4

• 1 : 2

• 1 : 1

• 1 : 5

Answer 1

Two radiations of photons energies 1 eV and 2.5 eV, successively illuminate a photosensitive metallic surface of work function 0.5 eV. The ratio of the maximum speeds of the emitted electrons is 1 : 2.

Explanation:

According to Einstein’s photoelectric effect, the K.E. of the radiated electrons

K.E_max = E - W

`1/2"mv"_1^2` = (1 - 0.5)eV = 0.5 eV

`1/2"mv"_2^2` = (2.5 - 0.5)eV = 2eV

`v_1/v_2=sqrt(0.5/2)=1/sqrt4=1/2`