E = pc

[Hannah Lee 2F]

When would we have to use the E = pc equation that is listed in the equations sheet and mentioned briefly in our notes? Can someone clarify for me in what problems/situations feature this equation? I don't think I've ever encountered it before in the homework.

[Caitlyn Tran 2E]

E=pc is just an equation that relates momentum with energy. We used it in our notes to show how when used in conjunction with E=hv (which relates energy to frequency), we can derive De Broglie's wave equation. I think that we would only use E=pc in a problem if we were given the velocity of an electron and expected to find energy or vice versa.

[TarynD_1I]

I think that you use E = pc when mass is not considered (maybe like a photon, because Lavelle said in class that photons do not have mass, but they have momentum).

[005206171]

E=pc is especially helpful to find the momentum of light which does not have rest mass (so you can't use p=mv). Light has no rest mass but does have momentum in the form of energy.