Total Internal Reflection
Total internal reflection explained in an easy to understand way:
Imagine you're trying to walk through a crowded room, but when you reach a particularly dense group of people, you're pushed back the way you came. This scenario is similar to total internal reflection, where light, instead of passing through the boundary into a different medium, is reflected back into the original medium. The crowded room is like the boundary of two materials, and just as you get redirected back because you can't get through, the light is reflected back because it can't cross the boundary at a certain angle.
Practice Version
Total Internal Reflection: Occurs when light hits the boundary between two materials but is reflected back. Total internal reflection. It is when light completely reflects inside a material instead of passing through, like light bouncing back into water from its surface.