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.

Answer 1

(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°`