Question

A beam of Light of wavelength λ is incident on a mirror at an angle θ. Find the change in momentum of the photon after reflection.

• A. $2\frac{h}{\lambda}\sin\theta$
• B. $\frac{h}{\lambda}\cos\theta$
• C. $2\frac{h}{\lambda}\cos\theta$
• D. None

Answer 1

Answer: (C)

$2\frac{h}{\lambda}\cos\theta$

Answer 2

∆p = 2p cos θ = 2 $\frac{h}{\lambda}\cos\theta$