Question 219: Wave Optics

Question

A source of light is placed in front of a screen. Intensity of light on the screen is I. Two Polaroids P
1
and P
2
are so placed in between the source of light and screen that the intensity of light on screen is I/2. P
2
should be rotated by an angle of (degrees) so that the intensity of light on the screen becomes $${{3I} \over 8}$$.

Accepted Answer

$$I = {{{I_0}} \over 2}{\cos ^2}\phi $$
$${{{I_0}} \over 2}{\cos ^2}\phi  = {{3I} \over 8}$$
$${\cos ^2}\phi  = {3 \over 4}$$
$${\cos ^2}\phi  = {{\sqrt 3 } \over 2}$$
$$ \Rightarrow \phi  = 30$$

Wave Optics

Integer / Numeric Answer Type