Malus law

When any source such as light bulbs or sun emit electromagnetic wave . the Electric field direction on the source is randomly generated by that result a unpolarized light . the E vector that generated on the source emission depends upon the direction of motion of charge particle which is completely random .. We use a polarizer to polarize unpolarized light . 



Working of Polarizer is very simple it cancel out all E-vector components except that parallel to axis of polarizer that a polarized light . 

Malus law relate intensity of polarized light after passing through polarizer with its previous intensity

Proof
We know intensity of light directly proportional to the square Amplitude .I.e
intensity of light directly proportional to the square Amplitude
consider the case of bellow image we have the angle between A vector and optical axis of polarizer is thita

Resolving those vectors components we have horizontal and vertical components 
Now using the above results we conclude that after passing through the polarizer we have amplitude
The above expression known as Malus law

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