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Wave Optics — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsWave Optics2 Marks
Question
Distinguish between polarised and unpolarized light. Does the intensity of polarised light emitted by a Polaroid depend on its orientation? Explain briefly.
The vibrations in a beam of polarised light make an angle of 60° with the axis of the polaroid sheet. What percentage of light is transmitted through the sheet?
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Answer

If the direction of vibration of electric field vector/plane of vibration of electric field vector, does not change with time, the light is polarised. Whereas, if the direction of vibration of electric field vector/plane of vibration of electric field vector changes randomly in very short intervals of time/with time, the light is unpolarised.

Yes, it depends upon orientation of Polaroid because electric field vibrations, that are not in the direction of pass axis of Polaroid, are absorbed. Hence, intensity changes. $I=I_0\cos^2\theta$ = angle between vibrations in light and axis of polaroid sheet) $I=I_0\cos^260^\circ=\frac{I_0}{4}$ $\Longrightarrow\frac{I}{I_0}\times100=\frac{1}{4}\times100=25\text{%}$

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