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Assertion: Polaroids are used to polaris...

Assertion: Polaroids are used to polarise as well as analyse place polarised light.
Reason: Polaroids reduce the intensity of light to zero.

Text Solution

Verified by Experts

Assertion is correct but reason is false. A polaroid allows those light vibrations to pass through it which are parallel to its axis.
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Two 'crossed' polaroids A and B are placed in the path of a light-beam. In between these, a third polaroid is C is placed whose polarisation axis makes an angel theta with a polarisation axis of the polaroid A. If the intensity of light emerging from the poloaroid a is I_(o) then show that the intensity of light emerging from polaroid B will be 1/4I_(o) sin^(2)theta.

(a) What is linearly polarised light ? Describe briefly using a diagram how sunlight is polarised (b) Unpolarised light is incident on a polaroid. How would the intensity of transmitted light change when the polaroid is rotated ?

Knowledge Check

  • Assertion: Nicol prism is used to produce and analyse plane polarised light. Reason: Nicol prism reduces the intensity of light to zero.

    A
    (a) If both assertion and reason are true and reason is the correct explanation of assertion.
    B
    (b) If both assertion and reason are true but reason is not the correct explanation of assertion.
    C
    (c) If assertion is true but reason is false.
    D
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  • Two crossed polaroids are placed in the path of a light beam. In between these a third polaroid is placed whose polarisation axis makes an angle phi with the polarisation axis of the first polaroid Then, intensity of light emerging from the third polaroid, in term of phi is

    A
    `(I_(0))/(4)sin^(2)2phi`
    B
    `(I_(0))/(4)sin^(2)phi`
    C
    `(I_(0))/(4)cos^(2)phi`
    D
    `(I_(0))/(2)cos^(2)2phi`

  • Assertion : Sound waves travelling in air cannot be polarised. Reason : Polarisation is property of light waves only.

    A
    If both assertion and reason are correct and reason is a correct explanation of the assertion.
    B
    If both assertion and reason and correct but reason is not the correct explanation of assertion.
    C
    If assertion is correct but reason is incorrect.
    D
    If assertion is incorrect but reason is correct.

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    (a) (i) How does an unpolarised light incident on a polaroid get polarised ? (ii) Describe briefly, with the help of a necessary diagram, the polarisation of light by reflection from a transparent medium. (b) Two polaroids 'A' and 'B' are kept in crossed position. how should a third polaroid 'C' be placed between them so that the intensity of polarised light transmitted by polaroid B reduces to 1/8th of the intensity of unpolarised light incidennt on A?

    (a) How does an unpolarised light incident on a polaroid get polarised ? Describe briefly, with the help of a necessary diagram, the polarisation of light by reflection from a transparent medium. (b) Two polaroids 'A' and 'B' are kept in crossed position. How should a third polaroid 'C' be placed between them so that the intensity of polarised light transmitted by polaroid B reduces to 1/8 th of the intensity of unpolarised light incident on A?

    What is meant by a linearly polarised light? Which type of waves can be polarised? Briefly explain a method for producing polarised light. Two polaroids are placed at 90^(@) to each other and the intensity of transmitted light is zero. What will be the intensity of transmitted light when one more polariod is placed between these two bisecting the angle between them ? Take intensity of unpolarised light as l_(0)

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    If there is zero absorption in the polaroid and if the intensity of plant-polarized light coming out of polaroid is A^2 , then the intensity of the incident beam will be

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