Total internal reflection

Definition

Total internal reflection occurs when a light ray traveling in a medium strikes an interface with another medium at an angle greater than or equal to the critical angle. Instead of refracting, the light is reflected back into the original medium.

Analogy

Imagine you are playing a game of billiards and you hit the cue ball towards the edge of the table. If you hit it too hard, it will bounce off and stay on the table. But if you hit it just right, it will bounce off at such an angle that it never comes back down and stays on the table forever. This is similar to how light can be trapped inside a medium due to total internal reflection.

Related terms

Critical Angle (θc): The minimum angle of incidence at which total internal reflection occurs.

Refraction: The bending or change in direction of light as it passes from one medium to another.

Prism: A transparent object with flat surfaces that can separate white light into its component colors through refraction.