Question

Three polaroid sheets are co-axially placed as indicated in the diagram. Pass axes of the polaroids 2 and 3 make 30° and 90° with pass axes of polaroid sheet 1. If \( I_1 \) is the intensity of the incident unpolarised light entering sheet 1, the intensity of the emergent light through sheet 3 is

• A. zero
• B. \( I_1 \cos^2 30^\circ \)
• C. \( \frac{I_1}{2} \)
• D. \( \frac{I_1}{4} \)

Answer 1

The Correct Option is C

According to Malus' Law, the intensity of light passing through a polarizer is given by:
\( I = I_0 \cos^2 \theta \)
where \( \theta \) is the angle between the light's polarization direction and the polaroid's transmission axis. 

The intensity decreases at each polaroid sheet according to the angle between the axes. After passing through all three polaroids, the intensity of the emergent light is \( \frac{I_1}{2} \), as each polarizer reduces the intensity by a factor related to the cosine of the angle between its axis and the polarization direction.