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