Physics · Science General

Optics and Light Properties

2,013 Questions

Optics and light properties focus on the behavior of light, including reflection, refraction, dispersion, and polarization. This topic also covers the wave nature of light, illumination, and the functioning of optical instruments like microscopes. Questions on these concepts are common in general science sections of SSC, Railways, and State exams.

Reflection and mirrorsRefraction and mediumsLight wave theoriesPolarization and intensity

Optics and Light Properties Questions

Multiple choice polarisation of light polarisation wave optics optics physics

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.

  1. $2.8$
  2. $9.4$
  3. $15.3$
  4. $10.2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice polarisation of light polarisation wave optics optics physics

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

  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 $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first polarizer reduces intensity to I0/2. The second polarizer is at angle theta to the first, so intensity becomes (I0/2) * cos^2(theta). The third polarizer is at 90 degrees to the first, meaning it is at (90-theta) to the second. Intensity = (I0/2) * cos^2(theta) * cos^2(90-theta) = (I0/2) * cos^2(theta) * sin^2(theta) = (I0/2) * (sin(2*theta)/2)^2 = (I0/8) * sin^2(2*theta).

Multiple choice polarisation of light polarisation wave optics optics physics

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 $\left(\mu _{water}=\dfrac{4}{3}\right)$.

  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. $\sin^{-1}\left(\dfrac{1}{3}\right)$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Brewster's law states that the angle of incidence for which reflected and refracted rays are perpendicular is given by tan(i) = n. Here, n = 4/3, so i = tan^-1(4/3).

Multiple choice polarisation of light polarisation wave optics optics physics

A polariser is used to :

  1. Reduced intensity of light

  2. Produced polarised light

  3. Increases intensity of light

  4. Produced unpolarised light
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A polarizer is an optical filter that lets light waves of a specific polarization pass while blocking light waves of other polarizations, effectively producing polarized light from unpolarized light.

Multiple choice polarisation of light polarisation wave optics optics physics

Two liner polarizers are crossed at an angle of ${ 60 }^{ \circ  }$. The fraction of intensity of light transmitted by the pair is

  1. $\dfrac { 1 }{ 4 } $
  2. $\dfrac { 1 }{ 8 } $
  3. $\dfrac { 3 }{ 8 } $
  4. $\dfrac { 1 }{ 2 } $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Unpolarized light passing through the first polarizer has its intensity halved (I1 = I0 / 2). The second polarizer is at an angle of 60 degrees to the first, so by Malus's law, the transmitted intensity is I2 = I1 * cos^2(60) = (I0 / 2) * (1 / 4) = I0 / 8.

Multiple choice polarisation of light polarisation wave optics optics physics

A polaroid making an angle ${ 60 }^{ \circ  }$ with electric vector then intensity reduced by a factor of:-

  1. $\dfrac { 1 }{ 4 } $
  2. $\dfrac { 3}{ 4 } $
  3. $\dfrac { 1 }{ 2 } $
  4. $\dfrac { 1 }{ 3} $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If a polarizer makes an angle of 60 degrees with the electric vector of polarized light, the intensity is reduced by a factor of cos^2(60) = (1/2)^2 = 1/4.

Multiple choice polarisation of light polarisation wave optics optics physics

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 plcaed between these polaroids then the intensity of light emerging from the last polaroid is 

  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 } }{ 4 } \right) { cos }^{ 4 }\theta $
  4. ${ I } _{ 0 }{ Cos }^{ 4 }\theta $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The derivation is identical to question 527898. The intensity is (I0/8) * sin^2(2*theta).

Multiple choice polarisation of light polarisation wave optics optics physics

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 :

  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. $I _ { 0 } \cos ^ { 4 } \theta$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is a repeat of the previous question. The intensity is (I0/8) * sin^2(2*theta).

Multiple choice polarisation of light polarisation wave optics optics physics

Optically active substances are those which

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

Multiple choice polarisation of light polarisation wave optics optics physics

Light transmitted in Nicol prism is

  1. unpolarized

  2. plane polarized

  3. circularly polarized

  4. elliptically polarized
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

Multiple choice polarisation of light polarisation wave optics optics physics

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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

Multiple choice polarisation of light polarisation wave optics optics physics

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 

  1. 3
  2. $\frac { 3 }{ 2 } $

  3. 1
  4. $\frac { 1 }{ 3 } $
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice polarisation of light polarisation wave optics optics physics

Optically active substances are those which

  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.
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

Multiple choice polarisation of light polarisation wave optics optics physics

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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