Give an answer to the following question: In the photoelectric effect, how can a photon moving in one direction eject an electron moving in a different direction? What happens to conservation of momentum?
Both momentum and energy are conserved in photoelectric effect. Photoelectric effect occurs in bound electrons and not in free electrons. Bound electrons are deep seated. When a photon encounters a bound electron it will deliver all its energy to the electron as a result of which the electron will receive energy to overcome the work function and also obtain some kinetic energy with which it can leave the metal surface.
Now the electron upon receiving the photon energy will move deeper into the layers of the metal, very less number of these electrons will get reflected back from these deeper layers, that's how the momentum is conserved. The photon direction is the same as the electron direction moving deeper into the metal layer. After getting reflected from the deeper layers without loosing much energy it will overcome the barrier potential or work function to come out of the metal and hence an electron will be ejected.
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