What is referred to as the critical angle in total internal reflection?

The critical angle is defined as the minimum angle of incidence at which total internal reflection occurs when light is traveling from a medium with a higher refractive index to one with a lower refractive index. When light hits the boundary between two different media at an angle greater than this critical angle, it cannot pass through the boundary and is instead reflected entirely back into the higher refractive index medium.

Understanding this concept is crucial in fields like fiber optics, where total internal reflection is employed to keep light contained within the core of a fiber optic cable, allowing signal transmission over long distances without loss of light.

The other responses do not accurately describe the critical angle. The angle at which light begins to diffract pertains to the wave nature of light and is related to diffraction rather than total internal reflection. The maximum angle of incidence for light to pass through is concerned with refraction, not reflection. Finally, the angle required for light absorption does not relate to the critical angle, as absorption involves energy transfer rather than the geometry of light pathways in different media.