A point source S emits unpolarized light uniformly in all directions. At two points A and B, the ratio $r = I_{A} / I_{B}$ of the intensities of light is 2. If a set of two polaroids having $45^{0}$ angle between their pass-axes is placed just before point B, then the new value of r will be _____.

see full answer

Start JEE / NEET / Foundation preparation at rupees 99/day !!

21% of IItians & 23% of AIIMS delhi doctors are from Sri Chaitanya institute !!

An Intiative by Sri Chaitanya

answer is 8.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

$I α \frac{1}{I^{2}}$
Where I: distance from point source.
$\Rightarrow \frac{I_{A}}{I_{B}} = \frac{I_{B}^{2}}{I_{A}^{2}} = 2$
$\Rightarrow I_{B} = \sqrt{2} I_{A} ......... (1)$
Also, due to polaroids: $\Rightarrow I_{B}^{'} = \frac{I_{B}}{2} \cos^{2} 45^{0} = \frac{I_{B}}{4}$
$\Rightarrow I_{B}^{'} = \frac{I_{B}}{4} ........ (2)$
Ratio becomes 4 times.
$\Rightarrow r_{n e w} = 8$