Tag: oscillations and waves

Questions Related to oscillations and waves

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

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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 $
$I _{t}=\dfrac{I _{0}}{2}\times \dfrac{1}{2}=\dfrac{I _{0}}{4}$

Two Polaroids $P _1$ and $P _2$ are placed with their axis perpendicular to each other. Unpolarized light $l _0$ is incident on $P _1$. A third polaroid $P _3$ is kept in between $P _1$ and $P _2$ such that its axis makes an angle $45^{\circ}$ with that of $P _1$. The intensity of transmitted light through $P _2$ is 

physics oscillations and waves polarization of light polarisation of light polarisation

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

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

  3. $\frac {I _0 }{8 }$

  4. $\frac {I _0 }{16 }$

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Correct Option: C
Explanation:
$I=I _0 .\cos^2 \theta$
$\theta =$ angle made by $E$ vector with transmission axis.wherein
$I=$ Intensity of transmitted light after polarisation.
$I _0=$Intensity of incident light.

Intensity of light after crossing $P _1=\dfrac {I _0}{2}$
Intensity of light after crossing $P _3=\dfrac {I _0}{2}.\cos^2 45^o =\dfrac {I _0}{4}$
Intensity of light after crossing $P _2=\dfrac {I _0}{4}.\cos^2 45^o$
$I=\dfrac {I _0}{8}$

Three polaroides are placed one above other, such that the first and the last polaroids are crossed with each other. If the angle between the transmission axis of the first two polaroids is $45$, then what is the percentage of incident light transmitted through the combination of three polaroids?

physics oscillations and waves polarization of light polarisation of light polarisation

  1. 0%

  2. 12.50%

  3. 50%

  4. 100%

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Correct Option: B

For a given medium, the polarising angle is $60^o$. What will be the critical angle for this medium?

physics oscillations and waves polarization of light polarisation of light polarisation

  1. $i = 35^o16'$

  2. $i = 45^o16'$

  3. $i = 55^o16'$

  4. $i = 65^o16'$

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Correct Option: A

A light has amplitude A and angle between analyzer and polarizer is.$60 ^ { \circ }$ Light is transmitted by analyzer has amplitude. 

physics oscillations and waves polarization of light polarisation of light polarisation

  1. $\mathrm { A } \sqrt { 2 }$

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

  3. $\frac { \sqrt { 3 } \mathrm { A } } { 2 }$

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

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Correct Option: B