Equations in Quantum [ENDORSED]

[amreen_sandhu1k]

Hi! I'm really confused about which equations can only be used for photons vs which can only be used for electrons would somebody mind differentiating the different equations for me? I understand the derivation of the equations but I still find myself using an equation meant only for electrons for photons.

[Chem_Mod]

Photons do not have mass so any equation that contains momentum (mass times velocity) cannot be used for photons because photons do not have mass.

[Hannah_Pon_1F]

Also, what sometimes helps me is breaking down the situation/context of the problem. For example, when looking at a problem with the photoelectric effect, because photons don't have mass you use E=hv to find the energy per photon this v= E/h to find the frequency. While if asked to find the frequency of the ejected e-, you could use the De Broglie formula because it accounts for mass and then convert to frequency.