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Q. What do you mean by polarisation of light.
Compare between interference and diffraction. Establish Brewster's law.
 

Dear Student
light is a elctromegnative wave that transmit such that it have motion is disstributed in mutually direction if we allowlight to propgate in  any one of the motion of light by using a polarizer when the light pass though polarizer is progate in only a defnite direction this phenomenonis called polarization of light 
 

Dear Student!!

Interference is the phenomenon of waves where waves from two different coherent sources superimpose at a given point and creates fringes.

The phenomenon of bending of light around the corners of an opaque object which obstructs the path of light is called diffraction.

It is due to diffraction we don’t see sharp shadows of objects; instead we see a penumbra region surrounding the umbra region of the shadow. Umbra is the darkest part of the shadow while penumbra is the part of the shadow which is partially illuminated.

Difference between interference and diffraction:

In interference pattern the intensity of dark fringe is completely zero. In diffraction pattern the intensity of secondary minima is minimum, but not completely zero.

In interference pattern the width of all the interference fringes is equal. In diffraction pattern the width of central maxima is large, and on increasing  distance , the width of maxima decreases.

In interference pattern the intensity of all the bright bands is equal. In diffraction pattern the intensity of all the secondary  maxima is not equal.

BREWSTER'S LAW::  WHEN UNPOLARIZED LIGHT OF GIVEN WAVELENGTH  IS INCIDENCE UPON TRANSPARENT SUBSTANCE IT EXPERIENCE MAX PLANE POLARISATION AT ANGLE OF INCIDENCE WHOSE TANGENT IS REFRACTIVE INDEX OF SUBSTANCE OF THAT WAVELENGTH
the angle of incidence for which angle between reflected and refracted ray becomes 90 degree  is called angle of polarisation.
in the  incidence ordinary light is reflected and becomes polarised light and refracted partially polarised light  as shown in fig below

now using snells law of refraction 
$$\begin{gathered} {\mu }_{air}\times \sin i ={\mu }_{medium}\times \sin r \\ 1\times \sin i ={\mu }_{medium}\times \sin r \\ now now r=90-i as shown in figure \\ 1\times \sin \left(i\right) ={\mu }_{medium}\times \sin (90-i) \\ \sin \left(i\right)={\mu }_{medium}\times \cos i \\ \tan i={\mu }_{medium} \end{gathered}$$

regards