> Fun fact: When you accelerate an electron across a potential of 4.5 volts, and then stop it suddenly, you get a photon with 4.5 electron volts of energy. That

> Fun fact: When you accelerate an electron across a potential of 4.5 volts, and then stop it suddenly, you get a photon with 4.5 electron volts of energy. That’s why different colors have different voltage drops. This explanation does violence to conservation of momentum, since \hbar / \lambda is miniscule for the photon compared to the electron. The correct explanation involves recombination with a hole across the bandgap, which is how momentum is conserved in the interaction, and the motion of the electron is not involved other than transport for electrons to find holes for recombining.