Are there any fields that affect light

In QFT, all fields interact with one another at some level.

Each particle is a quantum of the underlying field according to QFT so whenever 2 particles interact, their fields do as well loosely speaking. 

 

If you want an example, the electromagnetic field interacts with all electrically charged particles.

I have a question. When light bends due to gravity does light slow down or what. Cause I am wondering since mass produces gravitational field that extends to non zero everywhere in space. Even if it is a slight bit, light must always be bending in different directions, so why it doesn't slow down. Does it slow down is my question basically?

1 hour ago, Achilles said:

I have a question. When light bends due to gravity does light slow down or what. Cause I am wondering since mass produces gravitational field that extends to non zero everywhere in space. Even if it is a slight bit, light must always be bending in different directions, so why it doesn't slow down. Does it slow down is my question basically?

The local speed of light is always "c" but since the geodesic path it travels is obviously longer, the coordinate speed measured by a distant observer will appear to be slowed.

On martes, 21 de agosto de 2018 at 9:56 AM, Achilles said:

Are there any fields that affect light

Have you read something about electro-optical Kerr effect and magneto-optical Kerr effect?