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A plane polarized light is incident on a polariser with its pass axis making angle θ with x-axis, as shown in the figure. At four different values of θ, θ= 8^{\circ}, 38^{\circ}, 188^{\circ}and 218^{\circ}, the observed intensities are same. What is the angle between the direction of polarization and x-axis ?

  • Option 1)

    98^{\circ}

  • Option 2)

    128^{\circ}

  • Option 3)

    203^{\circ}

  • Option 4)

    45^{\circ}

 

Answers (1)

best_answer

As we learnt

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.

 

 I is same for \theta=8^{\circ},38^{\circ},188^{\circ},218^{\circ}

Only possible value is203^{\circ}

As

203^{\circ}-8^{\circ}=195^{\circ}\: \: (180^{\circ}+150^{\circ})

203^{\circ}-38^{\circ}=165^{\circ}\: \: (180^{\circ}-150^{\circ})

203^{\circ}-188^{\circ}=15^{\circ}

203^{\circ}-218^{\circ}=-15^{\circ}

 


Option 1)

98^{\circ}

Option 2)

128^{\circ}

Option 3)

203^{\circ}

Option 4)

45^{\circ}

Posted by

Avinash

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