What is total internal reflection?

• A. The bending of light when passing through a medium.
• B. The complete absorption of light in a medium.
• C. The complete reflection of light back into a medium.
• D. The scattering of light when it encounters particles.

Answer: (C)

Total internal reflection occurs when light traveling in a denser medium reaches the boundary of a less dense medium at an angle greater than the critical angle. At this point, instead of refracting into the less dense medium, the light is completely reflected back into the denser medium. This phenomenon is crucial in applications such as optical fibers, where light signals are kept within the fiber core through repeated total internal reflections, allowing for efficient transmission of data over long distances.

The other options describe different optical phenomena. The bending of light when passing through a medium relates to refraction, which occurs when light changes speed as it crosses into a medium of different density. Complete absorption refers to the scenario where light is entirely absorbed by a medium and does not exit, while scattering involves the redirection of light in various directions when it encounters particles. Understanding these distinct behaviors of light is essential in the study of optics, but total internal reflection specifically highlights the circumstances under which no light escapes into a less dense medium.