The correct answer to the question is option 3: total internal reflection.

Total internal reflection is the optical phenomenon that enables the propagation of light signals through an optical fiber. When light passes from a medium with a higher refractive index to a medium with a lower refractive index (such as from glass to air), it bends away from the normal line. However, when the angle of incidence is greater than the critical angle, all of the light is reflected back into the medium with the higher refractive index.

In the case of an optical fiber, the core (made of glass or plastic) has a higher refractive index than the cladding (outer layer). This means that when light enters the core at an angle greater than the critical angle, it undergoes total internal reflection and continues to propagate along the fiber. This phenomenon allows light signals to be transmitted over long distances without significant loss or distortion.

Interference (option 1) refers to the interaction of light waves, but it does not directly explain how light is transmitted through an optical fiber. Scattering (option 2) occurs when light interacts with particles or irregularities in a medium, leading to a deviation in its path. Refraction (option 4) is the bending of light when it passes from one