Question

Why do light get affected by gravity if photons have no mass?

Answer 1

     Light waves are electromagnetic waves. They contain energy. It is given by a formula = E = h f   , where h = Planck's constant.  f = frequency.

    This is possible by treating light as having a dual behaviour. Light behaves as a electromagnetic wave as well as tiny particles called photons traveling at a very high speeds.

   When particles have energy they could be treated as having mass too. Their energy can be converted into mass using the speed of light.  So when they have mass, they could be influenced by gravitational fields.

   Equations in quantum mechanics can be used to calculate the mass.  For example E = m c².

Answer 2

Answer:Photons have no mass, but they are nonetheless affected by gravity due to the bending of spacetime itself. In the presence of gravity, photons travel along geodesics. Geodesics depend on the geometry of spacetime and photons moving along a curved geodesic will appear to be affected by gravity. So the photons aren't exactly affected by gravity but instead because the mass warps the space-time through which the photons travel.

hope this helps