In a photoemission experiment X-ray photons with frequency hit a metal and are absorbed by an electron. After absorbtion these electrons have sufficient energy to escape the metal, but in doing so they have to give up an amount of energy W, called the work function.
All electrons have equal probability to absorb a photon.
When we see an object moving and we measure the length of this object to be L, we know that this value is smaller than the length measured by someone moving with the object. The relative length contraction is the quantity . Problem 3 Explain in a few sentences why covalent materials like Si and Ge are found in crystal structures where they have exactly four nearest neighbors. We do not know at which position inside the box it is. In this problem we can use the standard non-relativistic formulas for momentum and kinetic energy.