KCET · Physics · Wave Optics
Three polaroid sheets are co-axially placed as indicated in the diagram. Pass axes of the polaroids 2 and 3 make \(30^{\circ}\) and \(90^{\circ}\) with pass axis of polaroid sheet 1 . If \(I_0\) is the intensity of the incident unpolarised light entering sheet 1 , the intensity of the emergent light through sheet 3 is
- A zero
- B \(\frac{3 I_0}{32}\)
- C \(\frac{3 I_0}{8}\)
- D \(\frac{3 I_0}{16}\)
Answer & Solution
Correct Answer
(A) zero
Step-by-step Solution
Detailed explanation
Intensity of polarised light passing through first polaroid,
\(I_1=I_0 / 2\)
Intensity of light passing through second polaroid,
\(I_2=I_1 \cos ^2 \theta\)
\(=\frac{I_0}{2} \cos ^2 30^{\circ}=\frac{3}{4} I_0\)
Intensity of polarised light transmitted through third polaroid,
\(I_3=I_2 \cos ^2 \theta\)
\(=\frac{3}{4} I_0 \cos ^2 90^{\circ}\)
\(=\frac{3}{4} I_0 \times 0=0\)
\(I_1=I_0 / 2\)
Intensity of light passing through second polaroid,
\(I_2=I_1 \cos ^2 \theta\)
\(=\frac{I_0}{2} \cos ^2 30^{\circ}=\frac{3}{4} I_0\)
Intensity of polarised light transmitted through third polaroid,
\(I_3=I_2 \cos ^2 \theta\)
\(=\frac{3}{4} I_0 \cos ^2 90^{\circ}\)
\(=\frac{3}{4} I_0 \times 0=0\)
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