Reflection and Refraction

Reflection

Reflection is the change in direction of a wavefront at an interface between two different media
so that the wavefront returns into the medium from which it originated. For a smooth surface,
reflected light rays travel in the same direction. This is called specular reflection. For a rough surface, reflected light rays scatter in all directions. This is called diffuse reflection.

The laws of reflection are as follows:
a) The incident ray, the reflected ray and the normal to
the reflection surface at the point of the incidence lie
in the same plane.
b) The angle which the incident ray makes with the
normal is equal to the angle which the reflected ray
makes to the same normal.

Refraction

Refraction is the change in direction of propagation of a wave due to a change in its
transmission medium. For example, when we look at a straw in a glass of water, the straw
appears to be bent. You may have experienced the illusion, created by refraction effects, of the actual depth of a coin when you attempted to pick up the coin from a glass of water. The coin appears to be much closer to the surface than it actually is. The refraction occurs because light is traveling from a medium with higher density, which is water, to a medium with lower density that is air.

The refractive index or index of refraction (n) of a material is defined as:
n = c/v,
where c is the speed of light in vacuum and v is the speed of light in the medium.
For example, the refractive index of water is 1.333, meaning that light travels 1.333
times faster in a vacuum than it does in water.