NCERT · Class 10 · Science · Light – Reflection and RefractionDefine refraction of light. What is the fundamental cause of refraction?

Refraction of light is defined as the phenomenon of the bending of a light ray from its original straight-line path when it passes obliquely from one transparent medium into another transparent medium having a different optical density. The fundamental cause of this bending is the variation in the speed of light as it transitions from one medium to another. When light enters a denser medium, its speed decreases, causing it to bend towards the normal, and conversely, when it enters a rarer medium, its speed increases, bending away from the normal.