Fiber optic theory explains how light travels through thin strands of glass or plastic, known as fiber optics. This technology relies on the principle of total internal reflection, where light entering the fiber at a certain angle reflects off the walls, allowing it to travel long distances without significant loss of signal. In fiber optics, the core of the fiber carries the light, while the cladding surrounding it has a lower refractive index. This difference in refractive indices ensures that light remains trapped within the core. Fiber optic cables are widely used in telecommunications and internet connections due to their high speed and capacity.