Total internal reflection is a phenomenon that occurs when a light ray traveling through a denser medium reaches the boundary of a less dense medium at an angle greater than the critical angle. Instead of passing through the boundary, the light ray is reflected back into the denser medium, resulting in no light being transmitted through the boundary.
The critical angle is the angle of incidence at which a light ray traveling through a denser medium reaches the boundary of a less dense medium and undergoes total internal reflection. It is calculated by taking the inverse sine of the ratio of the refractive indices of the two media.
One common example of total internal reflection is the mirage effect seen on hot roads or deserts, where the light rays from the sky are reflected off the boundary between the hot ground and the cooler air, creating the illusion of water. Another example is the use of optical fibers, where total internal reflection is used to transmit light signals over long distances.
The angle of incidence, the refractive indices of the two media, and the smoothness of the boundary between the two media all affect total internal reflection. A larger difference in refractive indices and a smoother boundary increase the likelihood of total internal reflection occurring.
Total internal reflection has many applications in technology, such as in fiber optics, binoculars, and periscopes. It is also used in nature, such as in the eyes of certain animals that have a layer of reflective cells that allow them to see in dim lighting conditions.