Final answer:
Refraction occurs when light passes from one medium to another and changes direction due to a change in its speed.
Step-by-step explanation:
Refraction occurs when light passes from one medium to another and changes direction due to a change in its speed. The angle at which light enters the new medium determines the amount of refraction that occurs. So, the correct answer is light falls with an angle. When light passes through mediums that differ in optical density or light velocity, refraction occurs. Light falling perpendicularly does not cause any change in direction.
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