Physics 9702 · AS & A Level · Energy and momentum of a photon
Energy and momentum of a photon — practice question
An electron, while stationary, has mass $m_e$ and charge $-q$. A positron is a particle that, when at rest, has mass $m_e$ and charge $+q$. A positron then interacts with an electron. The electron and the positron can be treated as being at rest. The result of this interaction is that the electron and the positron turn into two gamma-ray ($\gamma$-ray) photons, each with the same energy.
(a(i))[2]
Calculate, for one of the $\gamma$-ray photons, the energy of the photon, in J.
(a(ii))[2]
Calculate, for one of the $\gamma$-ray photons, its momentum.
(b)[2]
State and explain the directions, 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: “$E = mc^2$” …