Tag: optics

Questions Related to optics

Two polaroids are placed in the path of unpolarized beam of intensity $I _ { 0 }$ such that no light is emitted from the second 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 polarids will be :

polarisation of light polarisation wave optics optics physics

  1. $\left( \dfrac { I _ { 0 } } { 8 } \right) \sin ^ { 2 } 2 \theta$

  2. $\left( \dfrac { I _ { 0 } } { 4 } \right) \sin ^ { 2 } 2 \theta$

  3. $\left( \dfrac { I _ { 0 } } { 2 } \right) \cos ^ { 4 } \theta$

  4. $I _ { 0 } \cos ^ { 4 } \theta$

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Correct Option: A

Which of the following is not an anisotropic?

polarisation of light polarisation wave optics optics physics

  1. zinc blend

  2. quartz

  3. sapphire

  4. iron oxide

  5. apatite

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Correct Option: A
Explanation:
Anisotropy is the property of being directionally dependent, which implies different properties in different directions.
Zinc blend (ZnS) is the only isotropic material in the list.
Quartz crystals and Saphire are birefringent, so they exhibit optical anisotropy.

The extraordinary waves in Iceland's spar

polarisation of light polarisation wave optics optics physics

  1. travel faster than speed of light

  2. travel slower than speed of light

  3. wave fronts follow laws of refraction.

  4. only ellipsoidal wave fronts observe laws of refraction

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Correct Option: D

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

polarisation of light polarisation wave optics optics physics

  1. a single dot.

  2. two stationary dots.

  3. two rotating dots.

  4. one dot rotating about the other.

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Correct Option: D
Explanation:

A dot which is shifted by some distance is appeared due to normal incidence and another dot is appeared which is rotating along with the crystal, when we see at a angle to the normal.
Hence option $D$ is correct .

Optically active substances are those which

polarisation of light polarisation wave optics optics physics

  1. produces polarized light

  2. rotate the plane of polarization of polarized light

  3. produce double refraction

  4. convert the plane polarized light into circularly polarized light

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Correct Option: B
Explanation:

The ability of a substance to rotate plane-polarized light is called optical activity and these substances are called optically active

Light transmitted in Nicol prism is

polarisation of light polarisation wave optics optics physics

  1. unpolarized

  2. plane polarized

  3. circularly polarized

  4. elliptically polarized

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Correct Option: B
Explanation:

In Nicol Prism, ordinary ray is eliminated and Extra-ordinary ray, which is plane polarized, is transmitted through the prism.

In, the case of linearly polarized light the magnitude of electric field vector

polarisation of light polarisation wave optics optics physics

  1. vary periodically with time

  2. increases and decreases linearly with time

  3. does not change with time

  4. is parallels to the direction of propagation

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Correct Option: A
Explanation:

In general equation for electric field vector for linearly polarized light is given as $\left| \vec { E }  \right| ={ E } _{ o }\sin { \left( { \omega t }-{ kx } \right)  } $ which indicate that its varies periodically with respect to time.

Such that it is perpendicular to the direction of propagation

Two beams, A and B of plane polartice light with mu;a;y perpendicular plances of po;arixation are seen triugh  polaroid from the position wjen the beam B has xero intensity a rotation of polato thorough 30 makes the two beams appear equally bright if the intial  Intensites of the two beams are 1 and 1 rtespctively the n equls 

polarisation of light polarisation wave optics optics physics

  1. 3

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

  3. 1

  4. $\frac { 1 }{ 3 } $

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Correct Option: A

Optically active substances are those which

polarisation of light polarisation wave optics optics physics

  1. produce polarized light

  2. rotate the plane of polarization of the polarized light.

  3. produce double refraction

  4. convert a plane polarized light into circularly polarized light.

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Correct Option: B
Explanation:

Optically active substance by definition are substances which can rotate the plane of polarization of polarized light.


Answer. B) rotate the plane of polarization of polarized light.

If for a calcite crystal, $\displaystyle\mu _0$ and $\displaystyle\mu _e$ are the refractive indices of the crystal for O-ray and E-ray repectively, then along the optic axis of the crystal

polarisation of light polarisation wave optics optics physics

  1. $\displaystyle\mu _0$ = $\displaystyle\mu _e$

  2. $\displaystyle\mu _0$ > $\displaystyle\mu _e$

  3. $\displaystyle\mu _0$ < $\displaystyle\mu _e$

  4. None of these

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Correct Option: A
Explanation:

In calcite crystal, only along the optical axis, the refractive indices of the crystal are equal for O-ray and E-ray