Physics · Science General

Optics and Light Properties

2,019 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

When sun light is incident on water at an angle of $ 53^o $ the reflected light is found to be completely plane-polarised. Determine : (i) angle of refraction of light,
(ii) refractive index of water.

  1. (i) $ 31^o $
    (ii) $ 1.427 $
  2. (i) $ 30^o $
    (ii) $ 2.327 $
  3. (i) $ 27^o $
    (ii) $ 1.327 $
  4. (i) $ 37^o $
    (ii) $ 1.327 $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Given i_p = 53 degrees. Angle of refraction r = 90 - 53 = 37 degrees. Refractive index mu = tan(53) = 1.327.

Multiple choice polarisation of light polarisation wave optics optics physics

The angle between polariser and analyser is $30 ^ { \circ }$  The ratio of intensity of incident light and transmitted by the analyser is

  1. 3:4

  2. 4:3
  3. $\sqrt { 3 } : 2$
  4. $2 : \sqrt { 3 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Given,
$\theta=30^0$
By using malus law,
$I=I _0cos^2\theta$
$\dfrac{I}{I _0}=(cos30)^2$
$\dfrac{I}{I _0}=(\dfrac{\sqrt{3}}{2})^2=\dfrac{3}{4}$
ratio, $I:I _0=3:4$
The correct option is A.
Multiple choice polarisation of light polarisation wave optics optics physics

The angle of incidence of light is equal to Brewster's angle, then 
A) Reflected ray is perpendicular to refracted ray
B) Reflected ray is parallel to refracted ray
C) Reflected light is polarized having its electric vector in the plane of incidence 
D) Refracted light is polarized.

  1. (A) and (D) are true

  2. (A) and (B) are true

  3. (A) and (C) are true

  4. (B) and (C) are true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At Brewster's angle, the reflected and refracted rays are perpendicular (A). The reflected light is polarized perpendicular to the plane of incidence (C is incorrect). The refracted light is partially polarized (D is correct).

Multiple choice polarisation of light polarisation wave optics optics physics

A beam of unpolarised light of intensity $I _{0}$ is passed through a polaroid $A$ and then through another polaroid $B$ which is oriented so that its principal plane makes an angle of $45^{\circ}$ relative to that of $A$. The intensity of the emergent light is

  1. $I _{0}$
  2. $I _{0}/2$
  3. $I _{0}/4$
  4. $I _{0}/8$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice polarisation of light polarisation wave optics optics physics

Polarizing angle for water is $53^o4'$. If light is incident at this angle on the surface of water and reflected the angle of refraction is:

  1. $53^o4'$
  2. $126^o56'$
  3. $36^o56'$
  4. $30^o4'$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

At the polarizing angle, i_p + r = 90 degrees. r = 90 - 53 degrees 4 minutes = 36 degrees 56 minutes.

Multiple choice polarisation of light polarisation wave optics optics physics

Which of the following cannot be polarised

  1. Radio waves

  2. UV rays

  3. IR rays

  4. Ultrasonic waves
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Polarization is a property of transverse waves. Ultrasonic waves are longitudinal waves and cannot be polarized.

Multiple choice polarisation of light polarisation wave optics optics physics

A beam of light strikes a piece of glass at an angle of incidence of $60 ^ { \circ }$ and the reflected beam is completely Plane polarised. Find the refractive index of this glass

  1. $\sqrt { 2 }$
  2. $\sqrt { 3 / 2 }$
  3. $\sqrt { 3 }$
  4. $\cfrac { 3 } { 2 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Refractive index mu = tan(i_p) = tan(60) = sqrt(3).

Multiple choice polarisation of light polarisation wave optics optics physics

If the polarizing angle for a given medium is $60^{\circ}$, then the refractive index of the medium is 

  1. $\dfrac{1}{\sqrt 3}$
  2. $\sqrt{\dfrac{3}{2}}$

  3. 2
  4. $\sqrt{3}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Refractive index mu = tan(i_p) = tan(60) = sqrt(3).

Multiple choice polarisation of light polarisation wave optics optics physics

A polarizer and an analyzer are arranged with their optic axes parallel to each other Symmetric light first passes through the polarizer and then the analyzer and the intensity of the light emerging is 'I'. If the analyzer is turned through $30^o$, the percent changes in the intensity is

  1. $75\%$
  2. $50\%$
  3. $25\%$
  4. $40\%$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Initial intensity I = I_0. After turning 30 degrees, I' = I_0 * cos^2(30) = I_0 * 3/4. The change is I_0 - 0.75I_0 = 0.25I_0, which is 25%.

Multiple choice polarisation of light polarisation wave optics optics physics

When unpolarized light beams are incidents in the air into glass ($n=1.5$ at polarising angle)

  1. reflected beams is $100$ polarised

  2. reflect and refracted beams are partially polarised

  3. the reason for (a) is that almost all the light is reflected

  4. all the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When unpolarized light is incident at Brewster angle from one medium to another, the light that is reflected from the surface is perfectly polarized

Multiple choice polarisation of light polarisation wave optics optics physics

Dichorism means

  1. selective absorption of unpolarised light.

  2. selective absorption of dispersed light.

  3. selective absorption of scattered light.

  4. selective absorption of one of the polarised component.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Dichromism is the selective absorption of one orthogonal polarization component of an incident beam over the other. this phenomenon is due to anisotropy of the material, with one polarization component experiencing preferential absorption.

Multiple choice polarisation of light polarisation wave optics optics physics

From Brewster's law, it follows that the angle of polarization depends upon

  1. the wavelength of light

  2. orientation of the plane of polarization

  3. orientation of the plane of vibration

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\theta _B=tan^{-1}\dfrac{n _2}{n _1}$

Since the refractive index for a given medium changes depending on the wavelength of light, Brewster's angle will also vary with wavelength.

Multiple choice polarisation of light polarisation wave optics optics physics

When unpolarized light is incidents on a plane glass plate at Brewster's angle, then which of the following statements is correct?

  1. Reflect and refracted rays are completely polarized with their planes of polarization parallel to each other.

  2. Reflect and refracted rays are completely polarized with their planes of polarization perpendicular to each other.

  3. Reflected light is the plane polarized but transmitted light is partially polarized.

  4. Reflected light is partially polarized but refracted light is plane polarized.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reflect and refracted rays are completely polarized with their planes of polarization perpendicular to each other.
option $B$ is correct