Question

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 intensity), a rotation of Polaroid through 30${}^o$ 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:

• A. $I$
• B. $I/3$
• C. $3$
• D. $3/2$

Answer 1

Answer: (B)

$I/3$

$I_{A}co{s}^{2}30=I_{B}co{s}^{2}60$
$\frac{I_A}{I_B}=\frac{1}{3}$