Answer:
This phenomenon is known as Refraction.
Step-by-step explanation:
Light waves change speed when they pass across the boundary between two substances with a different density, such as air and glass. This causes them to change direction, an effect called refraction.
At the boundary between two transparent substances:
the light slows down going into a denser substance, and the ray bends towards the normal
the light speeds up going into a less dense substance, and the ray bends away from the normal