Question

Two Polaroids (polarizers that can polarize visible light) are aligned so that the light passing through them is a maximum. At what angle should one of them be placed so that the intensity is subsequently reduced by half?

Answer 1

Let the intensity of light from the first polaroid is I_o

The intensity through the second polaroid is,

$I=I_{\text{o}}\cos ^2(\theta)$

where,

$\theta\text{ is the angle between the }direction\text{ of polarisation of two polaroids,}$

For the angle,

$\theta=45^{\circ}$

The intensity of light from the second polaroid is,

$\begin{gathered} I=I_o\cos ^2(45^{\circ}) \\ I=I_{\circ}(\frac{1}{\sqrt[]{2}})^2 \\ I=\frac{I_{\circ}}{2} \end{gathered}$

Thus, the intensity of light from the second polaroid becomes half if the angle between the direction of polarization of two polaroids is 45 degree.