A photon in light beam A has twice the energy of a photon in light beam B.The ratio p_A/p_B of their momenta is: A) 1/2 B) 1/4 C) 1 D) 2 E) 4

Question

Quizplus · Accepted Answer

The momentum of a photon is given by $p = \frac{E}{c}$, where $E$ is the energy of the photon and $c$ is the speed of light. If a photon in light beam A has twice the energy of a photon in light beam B, then its momentum will also be twice as much, because the speed of light $c$ is a constant. Therefore, the ratio of their momenta is $2:1$ or $2$.

A Photon in Light Beam a Has Twice the Energy