Question

How does the light have to enter the glass for no refraction to happen ?

Answer 1

Answer:

it has to enter at 90 degrees

Explanation:

at 90 degrees, there will not be any refraction as the the light will follow the same path

Answer 2

Answer: It has to enter at exactly 90 degrees.

Explanation: The reason is that refraction only happens when light enters another medium at a specific angle. At an angle the light will slow down and bend, like when the flow of water is less, it bends and comes out. If it comes perpendicular it will slow down, but will not appear to be changing direction.