Question: Q. 3. State Brewster’s law.
The value of Brewster’s angle for a transparent medium is different for light of different colours. Give reason.
R [Delhi 2016, 2015]
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Solution:
Ans. When unpolarised light is incident on the surface two media, the reflected light gets (completely) polarized only when the reflected light and refracted light become perpendicular to each other. 1 If the student draws the diagram, as shown, and writes $i_{B}$ as the polarizing angle, award this 1 mark. If the student just writes $\mu=\tan i_{B^{\prime}}$ award half mark only.
The refractive index of denser medium, with respect to rarer medium, is given by $\mu=\tan i_{B} \quad 1 / 2$ Since Refractive index ( $\mu$ ) of a transparent medium is different for different colours, hence Brewster’s angle is different for different colours.
[CBSE Marking Scheme 2016]
