I've been puzzled by this. If light of different frequencies (like ultra violet to infra-red) would experience different refraction angles in the presence of a powerful gravity field. I understand that light has zero rest mass but has effective mass given the fact it's in motion. What I'm figuring is it's frequency (I'm only guessing here) may yield a greater effective mass (eg, the ultra-violet over the infra-red) and that the two rays may refract at a slightly different angle due this? I'm a bit confused due to my knowledge of Newtonian vectors, and I only have a basic understanding of Relativity. Could someone explain this to me thanks, also is there a research paper about this thanks.