BioMedical Admissions Test (BMAT) 2025 – 400 Free Practice Questions to Pass the Exam

The term "critical angle" in optics specifically refers to the angle of incidence at which total internal reflection occurs when light is transitioning from a medium of higher refractive index (such as glass or water) to a medium of lower refractive index (like air). When the incidence angle exceeds this critical angle, all the light is reflected back into the denser medium rather than refracted out into the less dense medium.

This phenomenon occurs because as light travels from a denser to a less dense medium, the refraction angle increases until it reaches a maximum limit, which is defined as the critical angle. At this angle, the refracted light travels along the boundary between the two media, and any further increase in the angle of incidence results in total internal reflection.

In contrast, the other options relate to different aspects of light behavior but do not define the critical angle. The angle at which light enters a medium and the angle of refraction focus on how light bends at interfaces, while the angle between incident light and a reflective surface pertains to reflection rather than the transition between media and does not specifically describe the conditions for total internal reflection.