What happens during total internal reflection?

During total internal reflection, light must be moving from a denser medium to a less dense medium at an angle greater than the critical angle. When light attempts to exit a denser medium (like glass or water) to a less dense medium (like air), if it strikes the boundary at an angle larger than the critical angle, the light cannot refract into the less dense medium. Instead, it reflects entirely back into the denser medium. This phenomenon is critical in optics, particularly in the design of optical fibers, where the total internal reflection allows for light to be guided through the fiber without loss.

In contrast, light refracting at every boundary is not accurate in this context because total internal reflection only occurs under specific conditions. Moving from a less dense to a denser medium does not lead to total internal reflection; instead, light typically refracts into the denser medium. Lastly, light being absorbed completely by the medium contradicts the nature of total internal reflection, where light reflects rather than gets absorbed when conditions for total internal reflection are met.