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Question

# (a) How does one demonstrate, using a suitable diagram, that unpolarised light when passed through a polaroid gets polarized?(b) A beam of unpolarised light is incident on a glass-air interface. Show, using a suitable ray diagram, that light reflected from the interface is totally polarised, when μ=taniB, where μ is the refractive index of glass with respect to air and iB is the Brewster's angle.

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Solution

## (A) A polarizer transmits only a single orientation of linear polarization and blocks the rest of the light. For example, a polarizer oriented along X passes Ex and blocks EySome polarizers eliminate the non-passed polarization component (Ey in the above example) byabsorbing it, while others reflect this component. Absorbing polarizers are convenient when it isdesirable to completely eliminate one polarization component from the system. A disadvantageof absorbing polarizers is that they are not very durable and may be damaged by high-intensitylight (as found in many laser applications).(B). Indicate z-direction. ⟵⟶ Indicate (X-Y) electric field is perpendicular to the incident ray. From Snell’s law SiniB=μSinrB … (1) If reflected light and refracted light is perpendicular to each other then reflected light is completely polarized light. This is known as Brewster’s law.iB+900+r=1800∴r=900−iBby putting value of r in eq(1)SiniB=μCosiB∴taniB=μ

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