I had a simple question - how many different values can a photon present for spin angular momentum, given that it's spin is 1?
And although I immediately thought "3, since j = 2s + 1" (j being the quantum number for anuglar momentum) - I saw the question had a hint:
"remember that photons have zero mass."
So I googled a bit and found that photons can only have spins +1 or -1, and also that helicity was their "useful property" opposed to spin.
Then, after looking into "similar questions" I found this:
Spin 1 just means that the spin in any direction can assume values out of {-1,0,1}. The 0 is only possible for massive particles, so the photon can have spin -1 or +1. (...) By StackUser: tonydo
So apparently having no mass affects the behavior of a particle's angular momentum. I assume it has to do with Helicity? How does that make photons not have null values for angular momentum?
Because from the classical view, I'd expect zero angular momentum, much like one would expect zero linear momentum on a first analysis of massless bodies. But I am aware of p = h/lambda. Is helicity something like that?