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  • Please,please help me Unpolarized light of intensity I is incident on a system of two polarizers, A followedby B. The intensity of emergent light is I/2. If a third polarizer C is placed betweenA and B, the intensity of emergent light is reduced to I

Unpolarized light of intensity I is incident on a system of two polarizers, A followed
by B. The intensity of emergent light is I/2. If a third polarizer C is placed between
A and B, the intensity of emergent light is  reduced to I/3. The angle between the
polarizers A and C is θ. Then :

  • Option 1)

    \cos \Theta = \left ( \frac{2}{3} \right )^{1/2}

  • Option 2)

    \cos \Theta = \left ( \frac{2}{3} \right )^{1/4}

  • Option 3)

    \cos \Theta = \left ( \frac{1}{3} \right )^{1/2}

  • Option 4)

    \cos \Theta = \left ( \frac{1}{3} \right )^{1/4}

 

Answers (2)

best_answer

As we have learned

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.

 

both A and B should have same orientation of transmission axis only then we will have intentisity of I/2

let c makes angle \Theta with A then I/2\cos ^{2}\Theta \cdot \cos ^{2}\Theta = I/3

or 

\cos \Theta = (2/3)^{1/4}  

 

 

 


Option 1)

\cos \Theta = \left ( \frac{2}{3} \right )^{1/2}

This is incorrect

Option 2)

\cos \Theta = \left ( \frac{2}{3} \right )^{1/4}

This is correct

Option 3)

\cos \Theta = \left ( \frac{1}{3} \right )^{1/2}

This is incorrect

Option 4)

\cos \Theta = \left ( \frac{1}{3} \right )^{1/4}

This is incorrect

Posted by

Avinash

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