JEE Mains · Physics · STD 12 - Wave optics
- JEE Mains 2014
- Medium
- MCQ
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 \(\frac{{{I_A}}}{{{I_B}}}\)=
Pick an option to check your answer.
Answer & Solution
Correct Answer
(C) \(\;\frac{1}{3}\)
Step-by-step Solution
Detailed explanation
According to malus law, intensity of emerging beam is given by,
\(I=I_{0} \cos ^{2} \theta\)
Now, \(I_{A^{\prime}}=I_{A} \cos ^{2} 30^o\)
\(I_{B^{\prime}}=I_{B} \cos ^{2} 60^o\)
As \(I_{A^{\prime}}=I_{B^{\prime}}\)
\(\Rightarrow \quad I_{A} \times \frac{3}{4}=I_{B} \times \frac{1}{4}\) \(\therefore \quad \frac{I_{A}}{I_{B}}=\frac{1}{3}\)
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