Do photons have quantum mechanical wave functions like other particles do? If so, would I use some alternate version of Schrodinger's equation when deriving said wave function? I ask this because as we know, the Schrodinger equation is as follows: (-ħ2/2m)∇2 + v(x,y,z)Ψ = EΨ Photons however, have 0 mass, so m = 0. I'm sure the problem with this becomes obvious if you try to plug m = 0 into the equation. I can only think of one possible solution to this, and this is multiplying both sides of the equation by (-2m/ħ2). If you do that and then plug in m=0, then the equation simply becomes ∇2= 0 (which is solvable). Other than that, I don't see a solution. That is why I ask: Is there a Schrodinger equation or wave function for photons?