Question

What is the relation between the interaction parameter, ‘b’, and atomic radius, R, for the Pair Production?

(a) b > R

(b) b ≈ R

(c) b < R

(d) No relation between b and R

I have been asked this question in homework.

This key question is from Pair Productions in section Quantum Physics of Engineering Physics I

Answer 1

Correct answer is (c) b < R

Easy explanation: If b  < R, the photon is directly converted into an electron-positron pair, known as pair production.

 If b  > R, it means the interaction parameter is greater than the atomic radius. In this case, the electron is ejected by the photon and it is known as the Photoelectric effect.

 If b ≈ R, the incident photons are scattered by the electron of the atom and the electron itself gets scattered. This phenomenon is known as the Compton effect.