Which of the following phenomenon is used in optical fibers? (A) Reflection (B) Scattering (C) Total internal refraction (D) Interference

Optical fibers are thin strands of glass or plastic that transmit light signals over long distances. They work by transmitting light signals through several internal reflections within the fiber, thus allowing the signal to travel without significant loss of strength or distortion. The phenomenon responsible for this transmission needs to be identified among the given options.

(A) Reflection: Reflection occurs when light strikes a surface and bounces off. Though reflection does play a role in optical fibers, it is not the primary phenomenon responsible for the transmission of light. (B) Scattering: Scattering occurs when light encounters an imperfection or obstruction in its path, causing it to spread out in various directions. This is not desirable in optical fibers, as it causes signal loss and is not the primary mechanism for light transmission. (C) Total internal refraction: Total internal refraction (or total internal reflection, as it is commonly referred to) occurs when light hits a boundary at an angle greater than the critical angle, resulting in all the light being reflected within the medium without any transmission through the boundary. This is the key phenomenon that allows optical fibers to efficiently transmit light signals over long distances without significant loss or distortion. (D) Interference: Interference occurs when two or more light waves superpose to form a resultant wave. It primarily affects situations where multiple light sources are used or when different light paths overlap. Interference is not the primary mechanism responsible for light transmission within optical fibers.

Based on the analysis of each phenomenon, it is clear that total internal refraction (C) is the primary phenomenon used in optical fibers. So, the correct answer is (C) Total internal refraction.