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Brewster's law states that:
Tangent of polorising angle is equal to the refractive index of the medium.
μ = tan iP
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When a narrow beam of parallel light is passed through the polarrid and the polaroid is rotated about the incident light. If on rotating the polarrid through one complete rotation, there is no change in the intensity of emergent light in any position then the given light is unpolarised.
If there is no change in the intensity of the emergent light in one complete rotation of the polaroid the intensity becomes twice maximum and twice zero, then the given light is completely plane polarised.
If the intensity of the emergent light changes but never becomes zero, then the given light is partially polarised.
Polaroids are used in wind screen of the cars
A certain monochromatic light travelling in air is incident on a glass plate at a polarising angle. Angle of refraction in glass is found to be 32°. Calculate :
(i) the polarising angle;
(ii) refractive index, of glass.
Given:
∠ r = 32°
∠ ip= ?
ip + r = 90°
ip + 32 = 90°
∠ip = 58° , is the polarising angle.
(ii)
n = tan ip
n = tan 58
= 1.6 , is the refractive index of the glass.
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Mock Test Series
