1.

Unpolarised light of intensity 32Wm^-2 passes through three polarizers such that transmission axes of the first and second polarizer makes and angle 30^@ with each other and the transmission axis of the last polarizer is crossed with that of the first. The intensity of final emerging light will be

Answer»

(a) `32Wm^-2`
(b) `3Wm^-2`
(c) `8Wm^-2`
(d) `4Wm^-2`

Solution :Angle between `P_1` and `P_2=30^@(GIVEN)`
Angle between `P_2` and `P_3=theta=90^@-30^@=60^@`

The INTENSITY of LIGHT TRANSMITTED by `P_1` is
`I_1=I_0/2=32/2=16W/m^2`
According to Malus law the intensity of light transmitted by `P_2` is
`I_2=I_1cos^2 30^@=16(sqrt3/2)^2=12W/m^2`
Similarly intensity of light transmitted by `P_3` is
`I_3=I_2cos^2 theta=12 cos^2 60^@=12(1/2)^2=3W/m^2`


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