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  • A beam of plane polarised light of large cross-sectional area of uniform intenisty of 3.3 Wm-2 falls normally on a polariser (cross -sectional area <img alt="3 \times 10 ^{-4}m^{2}" src="http://entrancecorner.codecogs.com/gif.latex

A beam of plane polarised light of large cross-sectional area of uniform intenisty of 3.3 Wm-2 falls normally on a polariser (cross -sectional area 3 \times 10 ^{-4}m^{2}) which rotates about its axis with an angular speed of 31.4 rad/s. The energy of light passing through the polariser per revolution, is close to:
Option: 1 1.1 \times 10^{-5}J
Option: 2 1.0 \times 10^{-4}J
Option: 3 1.5 \times 10^{-4}J
Option: 4 5.0\times 10^{-4}J

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\begin{aligned} &\text{Given} \\ &\text { Intensity, } I=3.3 \mathrm{Wm}^{-2}\\ &\text { Area }= A=3 \times 10^{-4} \mathrm{~m}^{2}\\ &\text { Angular speed }= \omega=31.4 \mathrm{rad} / \mathrm{s}\\ &\text{now as we know}<\cos ^{2} \theta>=\frac{1}{2}, \text { in one time period }\\ &\therefore \text { Average energy }=\mathrm{I}_{0} \mathrm{~A} \times \frac{1}{2}=\frac{(3.3)\left(3 \times 10^{-4}\right)}{2}\simeq 5 \times 10^{-4} \mathrm{~J} \end{aligned}

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