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Question
Light from a sodium lamp (S) passes through two polaroid sheets P1 and P2 as shown in fig. What will be the effect on the intensity of the light transmitted (i) by P1 and (ii) by P2 on the rotating polaroid P1 about the direction of propagation of light? Justify your answer in both cases.
Solution
(i) There is no change in `I_1` on rotation of P1, because the intensity of light does not change irrespective of the orientation of pass - axis of the polaroid.
(ii) `I_1` = intensity of polarised light from P1
`I_2` = intensity of polarised light from P2
`theta` = Angle between pass axis of polaroid P1 and P2
by Malus's Law, `I_2 = I_1 cos^2 theta`
Thus `I_2` change when P1 is rotated as `theta` changes
`I_2 = 0, "when" theta = 90°`
`I_2 = I_1, "when" theta = 0°`
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