What is defined as the minimum angle of incidence for total internal reflection within a medium?

Total internal reflection occurs when a wave traveling through a medium hits the boundary of a less dense medium at a specific angle, resulting in the wave being reflected entirely back into the original medium rather than being refracted. The minimum angle of incidence that allows this phenomenon to occur is known as the critical angle.

The critical angle is determined by the refractive indices of the two media involved, which defines how much a light wave bends when passing from one medium to another. When the angle of incidence in the denser medium exceeds this critical angle, total internal reflection takes place. This concept is vital in various applications, such as optical fibers and periscopes, where maintaining light within a medium is crucial for efficient transmission.

Understanding the critical angle helps explain why certain angles lead to total internal reflection while others do not, further emphasizing its importance in optics.