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

(a) 1 : 4
(b) 1 : 2
(c) 1 : 1
(d) 1 : 5

Correct Answer:

1 : 2

Explanation:

According to the Einstein’s photoelectric effect, the K.E. of the radiated electrons
K.Eₘₐₓ = E – W
1/2 mv₁² = (1 – 0.5) eV = 0.5 eV
1/2 mv₂² = (2.5 – 0.5 eV = 2 eV
v₁ / v₂ = √ 0.5 / 2 = 1 / √4 = 1/2