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 the light is incident at the polarizing angle on transparent medium, then the completely polarized light is 

  1. refracted light

  2. reflected light

  3. refracted and reflected light

  4. neither reflected nor refracted light
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When the light is incident at the polarising angle on the transparent medium, the reflected light is completely polarised.

Multiple choice polarisation of light polarisation wave optics optics physics

The transverse nature of light is shown by

  1. interference of light

  2. refraction of light

  3. polarization of light

  4. dispersion of light
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Polarisation of light establishes that light are transverse in nature, otherwise it was believed that they are longitudinal waves, like the sound waves.

Multiple choice polarisation of light polarisation wave optics optics physics

Polarisation of light establishes

  1. corpuscular theory of light

  2. quantum nature of light

  3. transverse nature of light

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

Polarisation of light establishes that light are transverse in nature, otherwise it was believed that they are longitudinal waves, like the sound waves.

Multiple choice polarisation of light polarisation wave optics optics physics

A ray of light is incident on the surface of  a glass plate at an angle of incidence equal to Brewster's angle $\phi$. If $\mu$ represents the  refractive index of glass with respect to air, then the angle between the reflected and the refracted rays is

  1. 90$^o$ + $\phi$
  2. $sin^{-1}$( $ \mu cos \phi$)
  3. 90$^o$
  4. 90 $-sin^{-1}$ $\left (\displaystyle \frac{sin\phi }{\mu}\right )$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When angle of incidence is equal to the Brewster's angle then, the angle between reflected and refracted rays is $ { 90 }^{ o }$

Multiple choice polarisation of light polarisation wave optics optics physics

Human eye:

  1. can detect polarized light

  2. cannot detect polarization of light

  3. can detect only circularly polarized light

  4. can detect only linearly polarized light
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Polarization changes when plane of vibration of polarized light changes.
Human eye is insensitive to change in polarization and hence, cannot detect polarization of light.

Multiple choice polarisation of light polarisation wave optics optics physics

Polarisation of light was first successfully explained by:

  1. Corpuscular theory

  2. Huygens' wave theory

  3. Electromagnetic wave theory

  4. Planck's theory
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Electromagnetic wave theory explains light as being composed of electric field vibrating in planes.
Polarisation of light refers to vibrating electric field in a particular plane.

Multiple choice polarisation of light polarisation wave optics optics physics

When light is incident on a glass block at polarizing angle
a) reflected ray is plane polarized
b) reflected and refracted rays are perpendicular
c) reflected and refracted rays are partially polarized
d) refracted ray is partially polarised

  1. a, c and d are correct

  2. a, b and d are correct

  3. b, c and d are correct

  4. a, b and c are correct
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

when a beam of unpolarized light is incident on the glass block, certain amount of the incident vibration is reflected in a plane perpendicular to the plane of incidence and transmits the rest.
Thus reflected ray is completely polarized but not partially polarized.
Thus only (c) is wrong and rest options are correct.

Multiple choice polarisation of light polarisation wave optics optics physics

The polarising angle for glass is :

  1. same for different kinds of glass

  2. different for different kinds of glass

  3. same for lights of all colours

  4. varies with time
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Different kinds of glass have different refractive index. Thus as polarising angle depends on refractive index the polarising angle is different for different kinds of glass. $tan \ i = \mu $

Multiple choice polarisation of light polarisation wave optics optics physics

Bartholinus discovered :

  1. Interference by splitting the wave front

  2. Polarisation by reflection

  3. Polarisation by refraction

  4. Polarisation by double refraction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In 1669, another Danish scientist, Erasmus Bartholinus discovered the polarization of light by double refraction in Iceland spar (calcite).

Multiple choice polarisation of light polarisation wave optics optics physics

Choose the correct statements among the following given options.

  1. Brewster's angle is independent of wavelength of light.

  2. Brewster's angle is independent of the nature of reflecting surface.

  3. Brewster's angle is different for different wavelengths.

  4. Brewsters angle depends on wavelength but not on the nature of reflecting surface.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Brewster's angle is an angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface,
with no reflection.
$\theta _{B}=tan^{-1}(\dfrac{n _{2}}{n _{1}})$
$n _{2}$ refractive index of final medium
$n _{1}$ refractive index of initial medium
As different wavelength have different refractive indices the brewster angle is also different.

Multiple choice polarisation of light polarisation wave optics optics physics

Pile of plates can be used to produce completely polarised light due to :

  1. Reflection

  2. Refraction

  3. Double refraction

  4. A and B
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

pile of plates is used to produce plane polarized light by refraction.
By refraction through multiple plates vibrations in the plane of incidence are transmitted.
Thus we obtain a polarized light.

Multiple choice polarisation of light polarisation wave optics optics physics

At the polarising angle $(\theta _{B})$, angle of refraction is given by : 

  1. $90^{\circ}$
  2. $90^o+\theta _{B}$
  3. $90^o-\theta _{B}$
  4. $\dfrac{90^o}{\theta _B }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

At polarizing angle $\theta _{B}$
$\dfrac{sin \theta _{B}}{cos \theta _{B}}=\dfrac{sin \theta _{B}}{sin \gamma }$
we get $sin \gamma =cos \theta _{B}$
$sin \gamma =sin(90-\theta _{B})$
Thus $\gamma =90-\theta _{B}$

Multiple choice polarisation of light polarisation wave optics optics physics

The angle of incidence at which reflected light is totally polarised for reflection from air to glass (refractive index n) is :

  1. $sin^{-1}(n)$
  2. $sin^{-1}(1/n)$
  3. $ tan^{-1}(n)$
  4. $ tan^{-1}(1/n)$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The refractive index of glass is n
If the light is incident on the surface with an angle of incidence i given by tan i $=\mu $ using the Brewster's law the reflected light is completely polarized.
Here tan i $=n$
i$=tan^{-1}(n)$

Multiple choice polarisation of light polarisation wave optics optics physics

A light ray is incident on a transparent medium of $\mu =$ 1.732 at the polarizing angle. The angle of refraction is :

  1. 60$^{\circ}$
  2. 30$^{\circ}$
  3. 45$^{\circ}$
  4. 90$^{\circ}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Angle of incidence $=$ polarising angle
$tan i = \mu $
$tan i = 1.732$
$i = 60^{0}$
From snell's law
$\dfrac{sin i}{sin \gamma }=\mu $
$sin \gamma =\dfrac{sin 60^{0}}{1.732}$
$\gamma =30^{0}$

Multiple choice polarisation of light polarisation wave optics optics physics

The critical angle for total internal reflection for a substance is $45^{\circ}$. The polarizing angle for this substance is ($\tan 54^{\circ}44'=\sqrt{2}$) :

  1. $46^{\circ}16'$
  2. $54^{\circ}44'$
  3. $46^{\circ}44'$
  4. $54^{\circ}16'$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If polarizing angle is $\theta $
Then tan $\theta =\dfrac{1}{sin c}$
$tan \theta =\dfrac{1}{sin 45}=\sqrt{2}$
$\theta =54^{0}{44}'$