Tag: wave optics

Questions Related to wave optics

The Polaroid is :

polarisation of light polarisation wave optics optics physics

  1. Celluloid film

  2. Big crystal

  3. Cluster of small crystal arranged in a regular way

  4. Cluster of small crystals arranged in a haphazard way

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Correct Option: C
Explanation:

Polaroid consists of needle - like crystals aligned in a particular direction.
Thus option C is correct answer.

A calcite crystal is placed over a dot on a piece of paper and rotated. On seeing through the calcite, one will see : 

polarisation of light polarisation wave optics optics physics

  1. One dot

  2. Two stationary dots

  3. Two rotating dots

  4. One dot rotating about the other

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Correct Option: D
Explanation:

calcite crystal display an optical property called birefringence. This causes objects viewed through a clear piece of calcite to appear doubled.
This is the reason one will see one dot rotating about the other.

Consider the following statements A & B. Identify the correct choice in the given answers.
(A) The refractive Index of the extra-ordinary ray depends on the angle of incidence in double refraction
(B) The vibrations of light waves acquire onesidedness for both ordinary and extraordinary rays in double refraction

polarisation of light polarisation wave optics optics physics

  1. A & B are wrong

  2. A & B are correct

  3. A is correct B is wrong

  4. A is wrong B is correct

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Correct Option: B
Explanation:

In double - refraction the refractive index of the extra - ordinary ray varies according to the direction taken because it has components that  are both parallel and perpendicular to the crystal's optic axis. Thus (A) is correct.
The ordinary ray and the extraordinary ray are polarized in planes vibrating at right angles to each other. Thus (B) is correct.

If $\mu _{O}$ and  $\mu _{e}$ are the refractive indices of a double
refracting crystal, then
1)  $\mu _{O}$ < $\mu _{e}$ for quartz crystal
2)  ,$\mu _{O}$ > $\mu _{e}$ for calacite crystal

polarisation of light polarisation wave optics optics physics

  1. both 1 and 2 are true

  2. 1 is true 2 is false

  3. 1 false 2 is true

  4. both 1 and 2 are false

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Correct Option: A
Explanation:

For quartz crystal $\mu _{0}=1.544  ;  \mu _{e}=1.553$
For calacite crystal $\mu _{0}=1.658  ;  \mu _{e}=1.486$
Thus both a and b are true.

Huygens wave theory could not explain

polarisation of light polarisation wave optics optics physics

  1. reflection of light

  2. refraction of light

  3. interference of light

  4. double refraction

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Correct Option: D
Explanation:

Huygens waves theory could well explain reflection, refraction and interference of light but could not explain the double refraction because in huygens principle light is considered as mechanical wave which could not explain the double refraction.

The tourmaline crystal

polarisation of light polarisation wave optics optics physics

  1. Absorbs ordinary light and transmits extra ordinary

  2. Absorbs extra ordinary light and transmits ordinary light

  3. Both absorbs ordinary and extra ordinary light

  4. Both transmits ordinary light and extra ordinary light

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Correct Option: D
Explanation:

Some transparent crystals, such as tourmaline and calcite, have the property that when one views an object through them one sees two images of the object. If one passes a narrow beam of light through them, the refracted beam is split into two parts which travel through the crystal and emerge as two separate beams. One of the beams obeys the ordinary laws of refraction and is called the ordinary ray. The other beam is called the extraordinary ray. The extraordinary ray does not always lie in the plane of incidence. Its speed, and consequently its index of refraction, depends on its direction of propagation through the crystal.

Since the speed of the emerging rays and angle are different, the emergent rays are circularly or optically polarized.
Hence both ordinary and extraordinary light are transmitted.
The correct answer is option D.

What happens to electric field component when unpolarized light is incident on surface such that reflected and refracted light are at right angles?

polarisation of light polarisation wave optics optics physics

  1. Parallel component remains in reflected light

  2. Prependicular component remains in reflected
    light

  3. It will remain unpolarized

  4. Partially polarised reflected light.

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Correct Option: B

Two nicol prisms A and B are placed in the path of a beam of unpolarised light, so that no light emerges out of B. In between these two, a third nicol C is placed such that its principal section is at an angle of $30^0$ with that of A. The percentage of intensity of incident unpolarised light that emerges from B.

polarisation of light polarisation wave optics optics physics

  1. $2.8$

  2. $9.4$

  3. $15.3$

  4. $10.2$

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Correct Option: C

Two polaroids are placed in the path of unpolarized beam of intensity ${I _0}$ such that no light is emitted from the secong polaroid. If a third polaroid whose polarization axis makes an angle $\theta $ with the polarization axis of first polaroid, is placed between these polaroids then the intensity of light emerging from the last polaroid will be

polarisation of light polarisation wave optics optics physics

  1. $\left( {\frac{{{I _0}}}{8}} \right){\sin ^2}2\theta $

  2. $\left( {\frac{{{I _0}}}{4}} \right){\sin ^2}2\theta $

  3. $\left( {\frac{{{I _0}}}{2}} \right){\sin ^2}2\theta $

  4. ${I _0}{\cos ^4}2\theta $

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Correct Option: A

Unpolarized light is incident on a planet sheet of water surface. The angle of incident for which the reflected and refracted rays are perpendicular to each other is $\left(\mu _{water}=\dfrac{4}{3}\right)$.

polarisation of light polarisation wave optics optics physics

  1. $\sin^{-1}\left(\dfrac{4}{3}\right)$

  2. $\tan^{-1}\left(\dfrac{3}{4}\right)$

  3. $\tan^{-1}\left(\dfrac{4}{3}\right)$

  4. $\sin^{-1}\left(\dfrac{1}{3}\right)$

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Correct Option: C