# three identical polaroid sheet P1,P2 and P3 are oriented so that the pass axis of P2 and P3 are inclined at the angle of 60 and 90 respectivly with the pass axis of P1 . a monocromatic source S of unpolarised light of intensity I0 is kept in front of polaroid sheet P1 as shown in figure. determine the intensities of light as observed by the observer at O , when the polaroid P3 is rotated with respect to P2 at angle θ=30 and 60 degree.

When unpolarised light passed through P

_{1}then we will get intinsity $\frac{{I}_{0}}{2}$, its independent of angle.

$intensityoflightafterpas\mathrm{sin}gthrough{P}_{2}=\frac{{I}_{0}}{2}{\mathrm{cos}}^{2}60=\frac{{I}_{0}}{8}\phantom{\rule{0ex}{0ex}}Initiallyanglebetween{P}_{2}and{P}_{3}is30.Ifwerotate{P}_{3}atangle30\left(anticlockwise\right)withrespect{P}_{2}\phantom{\rule{0ex}{0ex}}.Atthistimeanglebetween{P}_{2}and{P}_{3}iszerothereforewegetintensity\phantom{\rule{0ex}{0ex}}\frac{{I}_{0}}{8}.\phantom{\rule{0ex}{0ex}}Ifwerotate{P}_{3}atangle60\left(anticlockwise\right)withrespect{P}_{2}.Atthistimeanglebetween{P}_{2}and{P}_{3}is30\phantom{\rule{0ex}{0ex}}Nowintensity=\frac{{I}_{0}}{8}{\mathrm{cos}}^{2}30=\frac{3{I}_{0}}{32}\phantom{\rule{0ex}{0ex}}Note:Ifunpolarisedorcircularlypolarizedlightpassedthroughpolariser\phantom{\rule{0ex}{0ex}}thenoutputintensityisindependentofanglebetweenpassaxis.$

Thank you

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