Final answer:
The question pertains to total internal reflection in physics, where light reflects entirely within a material when the refraction angle is 90 degrees due to the material having a higher index of refraction than the surrounding medium.
Step-by-step explanation:
The question seems to be related to the phenomenon of total internal reflection in physics, particularly as it pertains to optics and wave theory. The description provided indicates a situation when the interior material has a greater index of refraction than the surrounding material, and an incident ray of light approaches the boundary at the critical angle, causing the refracted ray to remain inside the material and reflect into the interior. This process, where the refracted angle is 90° and the ray does not leave the material, is what constitutes total internal reflection. Understanding this concept is crucial for applications such as fiber optics and certain imaging technologies.