Question

What is the unit for the coefficient of stimulated emission?

(a) s^-2

(b) m^3  s^-2

(c) J^−1 m^3

(d) J^−1 m^3  s^-2

I had been asked this question in class test.

I would like to ask this question from Einstein Coefficients topic in chapter Laser of Engineering Physics II

Answer 1

Correct answer is (d) J^−1 m^3  s^-2

Easiest explanation: For stimulated emission, the expression for the rate is B21uN2 where u stands for the energy density and N is the number of exited atoms. Therefore, the unit of B turns out to be J^−1 m^3  s^-2.