Two beams A and B, of plane polarized light with mutually perpendicular planes of polarization are seen through a polaroid. From the position when the beam A and has maximum intensity (and beam B has zero intensity). A rotation of polaroid through `30^(underset(-)(o))` 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))` equals.

Options

A. 1
B. `(1)/(3)`
C. `3`
D. `(3)/(2)`

Answer

B

Explanation

When polaroid is at angle `30^(underset(-)(@))` with beam A, it makes `60^(underset(-)(@))` with beam B by malus law
`Icos^(2)((phi)/(2))=I_(theta)cos^(2)60^(underset(-)(@))implies(I_(A))/(I_(B))=(1)/(3)`