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Thermal Radiation. Quantum Nature of Light.

Problem 5.288

A photon is scattered at an angle θ=120∘\theta=120^{\circ} by a stationary free electron. As a result, the electron acquires a kinetic energy T=0.45MeVT=0.45 \mathrm{MeV}. Find the energy that the photon had prior to scattering.

Reveal Answer
ℏω=[1+1+2mc2/Tsin⁡2(θ/2)]T/2=0.68MeV\hbar \omega=\left[1+\sqrt{1+2 m c^{2} / T \sin ^{2}(\theta / 2)}\right] T / 2=0.68 \mathrm{MeV}
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