What phenomenon confines light traveling down the core of an optical fiber?

The correct answer, total internal reflection, is fundamental to the operation of optical fibers. This phenomenon occurs when light travels from a medium with a higher refractive index (such as glass) to a medium with a lower refractive index (like air). If the angle of incidence is greater than the critical angle, the light does not pass into the air but instead is reflected entirely back into the high refractive index medium, effectively keeping the light confined within the optical fiber core.

This principle is what allows optical fibers to transmit light over long distances with minimal loss, enabling high-speed data transmission. The structure of the fiber—having a core surrounded by a cladding with a lower refractive index—facilitates total internal reflection, ensuring that light bounces within the core and travels along the length of the fiber.

The other options do not describe the mechanism that confines light within the fiber. Refraction describes how light bends as it travels from one medium to another, which is not the primary mechanism for guiding light in an optical fiber. Diffraction refers to the bending of waves around obstacles or openings, affecting how waves spread rather than confining light. Scattering involves the diffusion of light in various directions, which would lead to loss of intensity and does