Q. A radioactive nucleus of mass M emits a photon of frequency ν and the nucleus recoils. The recoil energy will be
A) hν
B) Mc² − hν
C) h²ν²/(2Mc²)
D) Zero
Explanation
[Solution from source] The photon carries momentum p = hν/c, and the nucleus recoils with equal and opposite momentum. Its kinetic energy is p²/2M = h²ν²/(2Mc²). It is not hν, which is the photon's own energy. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.