CBSE Class 12 Physics 2020 Delhi Set 1 Paper

Question : 23

Total: 37

Light from a sodium lamp (S) passes through two polaroid sheets P1 and P2 as shown in fig. What will be the effect on the intensity of the light transmitted (a) by P1 and (b) by P2 on rotating polaroid P1 about the direction of propagation of light? Justify your answer in both cases.

OR
Define the term 'wavefront of light'. A plane wave front AB propagating from denser medium (1) into a rarer medium (2) is incident on the surface P1P2 separating the two media as shown in fig.
Using Huygen's principle, draw the secondary wavelets and obtain the refracted wavefront in the diagram.

Solution:

(a) Intensity of the light at the output of I1=‌

since one component of light will be blocked.
(b) When this polarised light is passed through P2 the intensity of light at its output (I2) will be varying ( 0 to ‌

and again to 0 ) if P1 is rotated.
OR
Wavefront : Wavefront is an imaginary surface over which an optical wave has a constant phase.
Refraction of light from denser medium to rarer medium :

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