Final answer:
Total internal reflection requires the light to travel from a higher to a lower index of refraction and for the incident angle to exceed the critical angle.
Step-by-step explanation:
For total internal reflection to occur, two conditions must be satisfied:
- The light must travel from a medium with a higher index of refraction to a medium with a lower index of refraction (n1 > n2).
- The angle of incidence in the first medium must be greater than the critical angle for the pair of media involved.
The critical angle is the angle of incidence that results in the refracted angle being 90°, meaning the refracted ray grazes along the interface between the two media without entering the second medium. When this angle is exceeded, reflection rather than refraction occurs, and all the light is reflected back into the first medium. This phenomenon is utilized in fiber optics and endoscopes, where light is transmitted through fibers, avoiding loss through refraction by maintaining the conditions for total internal reflection.