Question

why the speed of light changes when light goes from one medium to another medium.​

Answer 1

Answer:

Speed slows down because in glass and water there is friction.

Answer 2

Answer:

Refraction is an effect that occurs when a light wave, incident at an angle away from the normal, passes a boundary from one medium into another in which there is a change in velocity of the light. Light is refracted when it crosses the interface from air into glass in which it moves more slowly.