Home
Class 12
PHYSICS
Two beams, A and B, of plane polarized l...

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 `30^(@)` makes the two beams appear equally bright. If the initial intensities of the two beams are `I_(A) and I_(B)` respectively, then `I_(A)// I_(B)` equals:

A

`(1)/(3)`

B

3

C

`(3)/(2)`

D

1

Text Solution

Verified by Experts

According to Malus' law, `I = I_(0)cos^(2) theta`
`therefore " " I_(A') = I_(A) cos^(2) theta_(1)`
`= I_(A)cos^(2) 30^(@) = (3)/(4) I_(A) " " [therefore theta_(1) = 30^(@)]`
Again, `I_(B') = I_(B)cos^(2) theta_(2) `
`= I_(B)cos^(2) 60^(@) = (1)/(4)I_(B) [because theta_(2) = 90^(@) - theta_(1) = 60^(@)]`
According to question, `I_(A') = I_(B')`
or, `(3)/(4)I_(A) = (1)/(4)I_(B) " " or, (I_(A))/(I_(B)) = (1)/(3)`
The option (A) is correct.
Doubtnut Promotions Banner Mobile Dark
|

Topper's Solved these Questions

  • DIFFRACTION AND POLARISATION OF LIGHT

    CHHAYA PUBLICATION|Exercise EXAMINATION ARCHIVE WITH SOLUTIONS (AIPMT)|3 Videos
  • DIFFRACTION AND POLARISATION OF LIGHT

    CHHAYA PUBLICATION|Exercise EXAMINATION ARCHIVE WITH SOLUTIONS (NEET)|3 Videos
  • DIFFRACTION AND POLARISATION OF LIGHT

    CHHAYA PUBLICATION|Exercise EXAMINATION ARCHIVE WITH SOLUTIONS (WBJEE)|1 Videos
  • CURRENT ELECTRICITY

    CHHAYA PUBLICATION|Exercise CBSE SCANNER|16 Videos
  • DIGITAL CIRCUITS

    CHHAYA PUBLICATION|Exercise CBSE SCANNER|6 Videos

Similar Questions

Explore conceptually related problems

Unplarised light is passed through a polaroid P_(1) . When this polarised beam passes through another polaroid P_(2) and if the pass axis of P_(2) makes angle theta with the pass axis of P_(1) , then write the expression for the polarised beam passing through P_(2) . Draw a plot showing the variation of intensity when theta varies from 0 to 2pi .

Two monochromatic coherent light beams A and B have intensities L and (L)/(4) respectively.If these beams are superposed the maximum and minimum intensities will be

Knowledge Check

  • A light beam is incident from air to a glass slab at Brewster's angle. A polaroid placed in the path of the reflected beam is being rotated about an axis passing through the centre and perpendicular to the plane of the polariod.

    A
    For a particular orientation there shall be darkness as observer sees through the polaroid
    B
    the intensity of light as seen through the polaroid shall be independent of the rotation
    C
    the intensity of light as seen through the polaroid shall go through a minimum but not zero for two orientations of the polaroid
    D
    the intensity of light as seen through the polaroid shall go through a minimum for four orientations of the polaroid
  • Similar Questions

    Explore conceptually related problems

    A narrow beam of unpolarised light of intensity I_(0) is incident on a polaroid P_(1) . The light transmitted by it is then incident on a second polaroid P_(2) with its pass axis making angle 60^(@) relative to the pass axis of P_(1) . Find the intensity of the light transmitted by P_(2) .

    The optic axis of two polaroids are inclined at an angle of 45^(@) with each other. Unpolarised light of intensity I_(0) being incident on the first polaroid emerges from the second polaroid. Find the intensity of the emergent light.

    Two polaroids A and B are kept in crossed position. How should a third polaroid C be placed between them so that the intensityof polarised light transmitted by polaroid B reduces to 1/8 th of the intensity of upolarised light incident on A?

    The optic axes of two polaroids are inclined at an angle of 45@ with each other. Unpolarised light of intensity I_0 being incident on the first polaroid emerges from the second polaroid. Find the intesity of the emergent light.

    Unpolarised light of intensity I passes through an ideal polariser A. Another identical polariser B is placed behind A. The intensity of light beyond B is found to be (I)/(2) . Now another identical polariser C is placed between A and B. The intensity beyond B is now found to be (I)/(8) . the angle between polariser A and C is

    Two polaroids P_(1) and P(2) are placed with pass axes perpendicular to each other. Unpolarised light of intensity I_(0) is incident on P_(1) . A thrid polaroid P_(3) is kept in between P_(1) and P_(2) such that its pass axis makes an angle of 45^(@) with that of P_(1) . Determine the intensity of light transmitted through P_(1) , P_(2) "and" P_(3).

    Two light beams of intersities I and 4I, respectively form interference fringes on a screen. For the two beams phase difference at point a is (pi)/(2) and at point B is pi . Find the difference in resultant intensities at A and B.