Unpolarised light of intensity 32 , W m^{-2} | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(D) Let the intensity of unpolarised light be $I_0 = 32 \, W m^{-2}$.After passing through the first polaroid,the intensity becomes $I_1 = \frac{I_0}{

Vedclass · Accepted Answer

$30$

Vedclass · Answer

(D) Let the intensity of unpolarised light be $I_0 = 32 \, W m^{-2}$.After passing through the first polaroid,the intensity becomes $I_1 = \frac{I_0}{2} = 16 \, W m^{-2}$.Let $	heta$ be the angle between the pass axis of the first and second polaroid.The intensity after the second polaroid is $I_2 = I_1 \cos^2 	heta = \frac{I_0}{2} \cos^2 	heta$.The angle between the second and third polaroid is $(90^{\circ} - 	heta)$ because the first and third polaroids are perpendicular.The intensity after the third polaroid is $I_3 = I_2 \cos^2(90^{\circ} - 	heta) = I_2 \sin^2 	heta$.Substituting $I_2$,we get $I_3 = \frac{I_0}{2} \cos^2 	heta \sin^2 	heta = \frac{I_0}{8} (2 \sin 	heta \cos 	heta)^2 = \frac{I_0}{8} \sin^2(2 	heta)$.Given $I_3 = 3 \, W m^{-2}$ and $I_0 = 32 \, W m^{-2}$,we have $3 = \frac{32}{8} \sin^2(2 	heta) = 4 \sin^2(2 	heta)$.$\sin^2(2 	heta) = \frac{3}{4} \implies \sin(2 	heta) = \frac{\sqrt{3}}{2}$.Thus,$2 	heta = 60^{\circ}$ or $120^{\circ}$,which gives $	heta = 30^{\circ}$ or $60^{\circ}$.

Similar Questions

In a system of two crossed polarisers,it is found that the intensity of light from the second polariser is half of that from the first polariser. The angle between their pass axes is (in $^{\circ}$)

Polarized glass is used for sunglasses because...

Two polarizers are placed such that the angle between their transmission axes is $60^o$. If unpolarised light of intensity $I_0$ is incident on the first polarizer,then the transmitted intensity from the second polarizer will be

Two polaroids are oriented with their planes perpendicular to incident light and transmission axis making an angle $30^{\circ}$ with each other. What fraction of incident unpolarised light is transmitted (in $\%$)? $(\cos 30^{\circ} = \sqrt{3} / 2)$

Vedclass Test Series

Exam Paper Generator

Online Exam Module