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 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 300 makes the two beams appear equally bright. If the initial intensities of the two beams are IA and IB respectively, then \frac{I_{A}}{I_{B}}  equals ::

 

  • Option 1)

    3

  • Option 2)

    \frac{3}{2}

  • Option 3)

    1

  • Option 4)

    \frac{1}{3}

 

Answers (1)

best_answer

As we learnt in

Malus Law -

I= I_{0}\cdot \cos ^{2}\theta

\theta = angle made by E vector with transmission axis.

- wherein

I= Intensity of transmitted light after polarisation .

I_{0}= Intensity of  incident light.

 

 We know that 

I_{A}cos^{2}30^{o}=I_{B}cos^{2}60^{o}

I_{A} \left(\frac{3}{4} \right )=I_{B} \left(\frac{1}{4} \right )

\therefore\ \; \frac{I_{A}}{I_{B}}=\frac{1}{3}

Correct option is 4.

 


Option 1)

3

This is an incorrect option.

Option 2)

\frac{3}{2}

This is an incorrect option.

Option 3)

1

This is an incorrect option.

Option 4)

\frac{1}{3}

This is the correct option.

Posted by

Aadil

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