How does light accelerate back to its original speed after refraction from another medium e.g. glass or water

Question

The speed of light slows as it traverses through a different medium, but after slowing it finds a way to accelerate back to original speed as it exits that medium. How does it do that?

In: 93

Answer 1

Something to keep in mind that any individual photon of light isn’t slowed down. But the medium absorbs and reemits the light causing an overall slowdown.

Think of it like taking a football and passing it through a crowded room. You can’t throw it through people so they have to catch the ball and throw it again. But get it the edge of the crowd and yeet it through open space there’s no more delay from catching and throwing again.