Question

State and proof brewster law with diagram ? Need detail answer

Answer 1

Brewster’s law, relationship for light waves stating that the maximum polarization (vibration in one plane only) of a ray of light may be achieved by letting the ray fall on a surface of a transparent medium in such a way that the refracted ray makes an angle of 90° with the reflected ray. The law is named after a Scottish physicist, Sir David Brewster, who first proposed it in 1811.

Brewster’s Law Brewster derived a relation amongst the polarizing angle ip and the refractive index mu which is well known as Brewster’s law. This says that the tangent of the polarizing angle is numerically equivalent to the refractive index of the medium.

A polarizing angle is created when at a certain angle of incidence, the reflected light is completely polarized, and this specific value of the angle of incidence is identified as polarizing angle. The polarizing angle ip hinges on on the refractive index mu of the transparent material.

The relation is articulated by “µ = tan ip”

When unpolarized light is found to be incident on a transparent medium at any polarizing angle then the transmitted and reflected rays are vertical to each other.

Answer 2

Brewster law states that-

When unpolarised light of suitable wavelength is incidence upon transparent substance it experiences maximum polarisation at the angle of incidence for which the angle between reflected ray and refracted ray is 90 degrees is called as angle of polarisation

Or

Tan of angle of polarisation is equal to refractive index of the medium

Proof-

Using snells law -

u(air)*Sin i = u(medium)*Sin r

1*Sin i = u(medium)*Sin r

Now r = 90-i as shown in figure

Sin i / Sin(90-i) = u(medium)

Sin i / cos i = u(medium)

tan i = u(medium)

Hence proved :)