Physics 9702 · AS & A Level · Energy and momentum of a photon
Energy and momentum of a photon — practice question
An electron has rest mass $m_e$ and charge $-q$. A positron is a particle with rest mass $m_e$ and charge $+q$ when at rest. An electron and a positron interact. They may be treated as stationary. As a result, the electron and positron are converted into two gamma-ray ($\gamma$-ray) photons, each with the same energy.
(a(i))[2]
Calculate the energy, in J, of one of the $\gamma$-ray photons.
(a(ii))[2]
Calculate the momentum, in N s, of one of the $\gamma$-ray photons.
(b)[2]
State and explain the direction, relative to one another, in which the $\gamma$-ray photons are emitted.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Appropriate use of $E = mc^2$” …