what is the physics principle behind fiber optics??

Total internal reflection?

http://en.wikipedia.org/wiki/Total_internal_reflection

The physics principle behind fiber optics is total internal reflection. Fiber optics uses the phenomenon of total internal reflection, which is a property of light when it encounters a boundary between two different materials.

To explain total internal reflection, let's consider a fiber optic cable, which is a long, thin strand made of glass or plastic. Inside the cable, there is a core surrounded by a cladding material. The core is where the light is transmitted, while the cladding is designed to reflect the light back into the core.

When light enters the core of a fiber optic cable, it bends due to a change in the refractive index between the core and the cladding. The refractive index is a measure of how much a medium slows down the light as it passes through it. It determines how much the light bends when it travels from one material to another.

The key concept here is that the refractive index of the core is higher than that of the cladding. This difference in refractive index causes the light to bend towards the center of the cable. If the angle at which the light enters the fiber is less than a certain critical angle (determined by the refractive indices of the core and cladding), the light will continue traveling through the core without escaping. However, if the angle of incidence exceeds the critical angle, the light will be completely reflected back into the core.

By repeatedly bouncing the light off the cladding through total internal reflection, the fiber optic cable is able to transmit light signals over long distances with very little loss in intensity. This property of total internal reflection allows fiber optics to transmit light signals in the form of data at incredibly fast speeds, making it an essential technology in telecommunications, internet connectivity, and many other applications.

In summary, fiber optics applies the principle of total internal reflection to guide and transmit light signals through a fiber optic cable efficiently.