A radioactive nucleus of mass M emits a photon of frequency v and the nucleus recoils. The recoil energy will be

Options

(a) Mc² – hv
(b) h²v² / 2Mc²
(c) zero
(d) hv

Correct Answer:

h²v² / 2Mc²

Explanation:

Momentum Mu = E/c = hv / c
Recoil energy
1/2 Mu² = 1/2 . M²u² / M = 1/2M (hv/c)²
= h²v² / 2Mc²