Question

A photocathode has a work function of 2.4 eV. It is illuminated with a monochromatic radiation whose photon energy is 3.9 eV. The maximum kinetic energy of the photoelectrons produced is:
1. 2.4 × 10^-19 J
2. 3.7 × 10^-19 J
3. 4.6 × 10^-19 J
4. 7.2 × 10^-19 J

Answer 1

Correct Answer - Option 1 : 2.4 × 10^-19 J

Work function (ϕ₀) is the minimum energy required to remove an electron from the surface of the material.

(kE)_max = hν – ϕ₀

Now here, Photon energy = 3.9 eV

Work function (ϕ₀) = 2.4 eV.

(k.E)_max = 3.9 – 2.4 = 1.5 eV

= 1.5 × 1.6 × 10^-19 J = 2.4 × 10^-19 J