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 has maximum intensity (and beam B has zero ntensity), a rotation of polaroid through `30^circ` 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:

Answer

A

Explanation

When a polaroid rotted through `30^(@)` with respect to beam A, then beam B is at `60^(@)` with it. So,
`l_(A)cos^(2)30^(@)=l_(B)cos^(2)60^(@)`
`=l_(A)((3)/(4))=l_(B)((1)/(4))implies(l_(A))/(l_(B))=(1)/(3)`