Refraction and refractive index

Refraction can be defined as the bending of a wave as it crosses the boundary between two medium. This takes place for all forms of waves including light.

Why refraction occurs?
Refraction occurs because there is a change in velocity between both medium.

Refractive index

Refractive index can be defined as a constant that gives the degree to which refraction or bending of a wave takes place between the two medium.
Here are the formulas associated with refractive index:

• Snell's Law

         n= sin i ÷ sin r

• n = incident velocity ÷ refractive velocity

• n= incident wavelength ÷ refractive wavelength

n => refractive index
i => angle of incidence
r => angle of refraction

• anb = 1 / bna

'a' and 'b' are the different mediums.


Where do waves bend with respect to the normal?

When waves are entering a denser medium they bend toward the normal but when entering a less dense medium they bend away from the normal.

What happens to light when it meets a boundary perpendicularly?

Refer to the diagrams below. When the wave meets the boundary perpendicularly it is not diffracted it just goes straight through.