1.

Two beams, A and B of plane polarised light with mutually perpendicular plane of polarisation are seen through a polaroid. From the position when the beam A has maximum intensity (and beam B has zero intensity) a rotation of polaroid through 30^(@) makes the two beams appear equally bright. If the initial intensities of the two beams are I_(A) and I_(B) respectively, then (I_(A))/(I_(B))=.....

Answer»

`(3)/(2)`
1
`(1)/(3)`
3

Solution :Let the MAXIMUM intensities of beam A and beam B are `I_(A) and I_(B)` respectively. Both beams have same intensity now B POLAROID rotates by `30^(@)`
`:.I_(A)cos^(2)30^(@)=I_(B)cos^(2)60^(@)`
`:.(I_(A))/(I_(B))=(cos^(2)60^(@))/(cos^(2)30^(@))=(((1)/(2))^(2))/(((SQRT(3))/(2))^(2))`
`:. (I_(A))/(I_(B))=(1)/(3)`


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