As far as I know, according to current theories and observations, the speed of light is a strange physical quantity. No matter you run at any speed, the speed of light you observe is the same, so whether you are in different magnetic fields or not, the speed of light should be constant (this is based on the conclusion of current theory)

In fact, people have long raised some questions about the speed of light. Is it the same speed as matter? If people travel in the opposite direction to the light beam, isn't the relative speed of light to people faster than the speed of light? But the experimental results of astronauts show that the speed of light measured in space is the same as that measured on the ground.

Personally, I think the wave-particle duality of light is just a hypothetical theory that simply explains the photoelectric effect. In fact, light is an energy wave, which appears in the form of wave packets. I read the book of Japanese photoelectric elements in my early years. More directly, the Doppler effect will occur when light is electromagnetic wave, but the speed of light itself will not change.

In addition, we cannot observe the boundary quality of light waves, which leads to the hypothesis of wave-particle duality. Personally, I think there must be a connection point and relationship between electricity, magnetism and gravity. However, the unified field theory has not met us yet. If the unified field theory exists, the magnetic field will produce a gravitational field. According to the theory of relativity, the gravitational field will change the spatial structure, and light may change its path (slightly bend), but at this stage, the theory cannot prove that the speed of light will be changed.

The following is my personal guess: electromagnetic waves may interfere with light and cause spectral changes. But it is the same as the electromagnetic wave itself. Under no circumstances will the wave velocity change.