Light is described by rays that travel in straight lines in an isotropic and homogeneous medium. When the ray strikes an interface between the two media, its direction gets changed. At the interface both the reflection and the refraction take place. Change of direction in the same medium due to strike at the interface is known as reflection, while the change of direction in the second medium is known as refraction.
An isotropic and homogenous medium is characterised by the refractive index which is a measure of velocity of light in that medium. The medium has different refractive indices for light of different colors.
The reflection and refraction of light at the interface are described by law of reflection and law of refraction. These laws are the foundation of geometrical optics. The propagation of rays and also the image formation by lenses and mirrors etc. are governed by these laws.
Under certain conditions, explained later, the ray instead of refracting gets totally reflected. This phenomenon is known as total internal reflection and plays a very important role in light guidance through fibers.
This section presents the study of the phenomenon interactively. Input parameters, the refractive indices of the two media and the angle of incidence can be varied and the propagation of light can be studied.
This section presents the interactive study of the light propagation through the fibers. By varying the refractive indices of the medium in front of the fiber, medium inside the fiber, medium of the cladding of the fiber and the angle of incidence, the passage of light in the meridional plane through the fiber can be traced.