Tag: polarisation of light

Questions Related to polarisation of light

Which one is not produced by sound waves in air?

physics wave optics polarization of light polarisation of light polarisation

  1. Polarisation

  2. Diffraction

  3. Refraction

  4. Reflection

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Correct Option: A
Explanation:

As sound waves are longitudinal waves, they don't exhibit Polarization phenomenon, which is exhibited by the transverse wave only.

A point source of monochromatic light is situated at the centre of a circle, what is the phase difference between the light waves passing through the end points of any diameter

physics wave optics polarization of light polarisation of light polarisation

  1. $\dfrac{\pi}{2}$

  2. $\pi$

  3. $\dfrac{3\pi}{2}$

  4. $zero$

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Correct Option: D

An unpolarised light of intensity $32  \mathrm{W} / \mathrm{m}^{2}  $ passes through three polarisers, such that the transmission axis of last polarizer is perpendicular with the first. If the intensity of emergent light is $3  \mathrm{Wh}  $ Im $ ^{2} $ then the angle between the transmission axes of the first two polarisers is:

physics wave optics polarization of light polarisation of light polarisation

  1. $ 30^{\circ} $

  2. $ 19^{\circ} $

  3. $ 45^{\circ} $

  4. $ 90^{\circ} $

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Correct Option: A

Two polaroids are oriented with their transmision axes making angle of $30^{\circ}$ with each other. The fraction of indicent unpolarised light is transmitted.

physics oscillations and waves polarization of light polarisation of light polarisation

  1. $37\%$

  2. $37.5\%$

  3. $3.36\%$

  4. $36.5\%$

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Correct Option: B

The axes of the polarizer and analyzer are inclined to each other at an angle of $60^{o}$. If the amplitude of polarized light emerging through the analyzer is $A$, the amplitude of unpolarized light incident on the polarizer is

physics oscillations and waves polarization of light polarisation of light polarisation

  1. $A/2$

  2. $A$

  3. $2A$

  4. $2\sqrt{2}\ A$.

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Correct Option: D

Unpolarised light of intensity $I _{0}$, is passed through a polarizer. What is the intensity of the transmitted light ?

physics oscillations and waves polarization of light polarisation of light polarisation

  1. $I _{0}\cos^2\theta$

  2. $2I _{0}\cos^2\theta$

  3. $I _{0}\cos^2\theta/2$

  4. $2I _{0}\cos^2\theta2$

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Correct Option: A

Two polorides are placed having their transmission axis at an angle of $45^0$. If unpolarised light is incident on first polorid acting as polarizer then, calculate intensity of emergent light from second polariser:-

physics oscillations and waves polarization of light polarisation of light polarisation

  1. $I _0$

  2. $\frac{I _0}{4}$

  3. $\frac{I _0}{2}$

  4. $2I _0$

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Correct Option: B

Plane polarized light is passed through a Polaroid. Now the Polaroid is given one complete rotation about the direction of light propagation. When viewed through another Polaroid (analyser), one of the following is observed:

physics oscillations and waves polarization of light polarisation of light polarisation

  1. The intensity of light gradually decreases to zero and then remains zero

  2. The intensity of light becomes twice maximum and twice zero

  3. The intensity of light becomes maximum and stays maximum

  4. The intensity of light does not change

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Correct Option: B
Explanation:

The Intensity of light coming out of a polaroid is
given by $I=I _{0}  cos^{2}\theta $
when $\theta $ is changed to $\theta +2\pi $  by rotation
$cos^{2}\theta$ becomes 1 twice at $\pi $ and $2\pi $ and
o twice at $\pi /2$ and $3\pi /2$
Thus option B is correct.

When an unpolarised light is polarized, then the intensity of light of the polarized wave :

physics oscillations and waves polarization of light polarisation of light polarisation

  1. remains the same

  2. gets doubled

  3. gets halved

  4. depends on the colour of the light.

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Correct Option: C
Explanation:

In an unpolarised light the light has Intensity distributed in all polarizing directions.
When it is polarized half the Intensity is polarized in a particular direction and the other half in a perpendicular direction is not transmitted.

Unpolarized light of intensity $I _{0}$ is incident on a polarizer and the emerging light strikes a second polarizing filter with its axis at 45$^{\circ}$ to that of the first. The intensity of the emerging beam :

physics oscillations and waves polarization of light polarisation of light polarisation

  1. $\dfrac{I _{}o}{2}$

  2. $\dfrac{I _{}o}{4}$

  3. $I _{o}$

  4. $\dfrac{I _{}o}{3}$

Show answer
Correct Option: B
Explanation:

The unpolarized light of Intensity $I _{0}$ is incident on a polarizer then a polarized light at intensity $I _{0}/2$ comes out.
Intensity of transmitted beam
$I _{t}=I _{0}/2 cos^{2} 45$ from the formula $I=I _{0} cos^{2} \theta $
$I _{t}=\dfrac{I _{0}}{2}\times \dfrac{1}{2}=\dfrac{I _{0}}{4}$