1. Jan 13 th Posters due Friday Interactions of Photons with matter

2. The Compton Effect In the 1920s, Compton was doing experiments with x-rays. He realized that when he fired x-rays at metal foil, he would detect lower energy x-rays coming out of the foil at different angles. This is called Compton scattering. He wondered if the x-rays might be undergoing elastic collisions in which momentum was conserved. But how can EM radiation have momentum if it has no mass? Derivation

4. Reflection Photons also interact with matter when they reflect off a surface. This is a perfectly elastic collision. Photoelectric Effect We saw yesterday how high enough energy photons can free electrons from their atoms and cause a current to flow

5. Absorption A photon can also interact with an atom, causing the electrons orbiting the nucleus to jump up to the next electron shell. Pair Production Yet another way that photons can interact with matter is through pair production. A high enough energy photon, when colliding with a nucleus, can cause an electron and a positron (anti-matter electron) to be created

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