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

Optically active substances are those substances which 

  1. produces polarised light

  2. produces double refraction

  3. rotate the plane of polarisation of polarised light

  4. converts a plane polarised light into circularly polarised light
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

By definition, optically active substances are those which can rotate the plane of polarisation of polarised light.

Multiple choice polarisation of light polarisation wave optics optics physics

Polaroid glass is used in sun glasses because

  1. it reduces the light intensity to half on account of polarisation

  2. it is fashoinable

  3. it has good colour

  4. it is cheaper
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Polaroid glass cut glare and haze by reducing the light intensity to half on account of polarisation, so that eyes are more comfortable and viewer can see better, therefore they are used in sun glasses.

Multiple choice polarisation of light polarisation wave optics optics physics

A nicol prism is based on action of

  1. refraction

  2. double refraction

  3. dichroism

  4. both (b) and (c)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When a ray of light enters nicol prism, it splits into two plane polarised light in mutually perpendicular direction. One of this light undergoes total reflection and absorption whereas other comes out as a plane polarised light.

Multiple choice polarisation of light polarisation wave optics optics physics

If a polaroid is kept in the path of an uniformly unpolarised light, the intensity of the transmitted light to the intensity of the light when the polaroid was not kept in its path is.

  1. 1
  2. $\dfrac{1}{2}$
  3. $\dfrac{1}{\sqrt 2}$
  4. $\dfrac{1}{2\sqrt 2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The component of the electric vector of all the electric vectors of unpolarised light in one direction only = $\dfrac {E _0}{\sqrt {2}} $
And, $I \propto E^2 \Rightarrow I = \dfrac {I _0}2 $
Multiple choice polarisation of light polarisation wave optics optics physics

A Nicol prism can be used.

  1. For producing and analysing polarised light

  2. Only to analyse polarized light

  3. Only to produce polarized light

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A Nicol prism is use to produce and analyse the polarised light.

Multiple choice polarisation of light polarisation wave optics optics physics

The angle of incidence at which reflected light is totally polarized form aim is :

  1. $\sin ^ { - 1 } ( n )$
  2. $\sin ^ { - 1 } \left( \frac { 1 } { n } \right)$
  3. $\tan ^ { - 1 } \left( \frac { 1 } { n } \right)$
  4. $\tan ^ { - 1 } ( n )$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Brewster's law states that the angle of incidence i for which reflected light is totally polarized is given by tan(i) = n, where n is the refractive index.

Multiple choice physics energy production perfectly black body black-body radiation black body radiation

A blackbody does not

  1. emit radiation

  2. absorb radiation

  3. reflect radiation

  4. refract radiation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An ideal blackbody is defined as an object that absorbs all electromagnetic radiation that falls on it, regardless of frequency or angle of incidence. Because it absorbs everything, it does not reflect any radiation.

Multiple choice

What is a photon?

  1. A measurement of color temperature

  2. A Pixel

  3. A made up word

  4. Particle of light
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A photon is the fundamental particle of light. It is a quantum of electromagnetic radiation.

Multiple choice physics static electricity properties of charges charge properties of charge

Electron accelerated by potential $V$ are diffracted from a crystal. If $d=1 A$ and $i = 30^\circ $. $V$ should be about  $h = 6.6 \times {10^{ - 24}}Js\,{m _e} = 9.1 \times {10^{ - 33}}kg.e = 1.6 \times {10^{ - 19}}C$

  1. $2000 V$
  2. $50 V$
  3. $500 V$
  4. $1000 V$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$d=1A$

$i={ 30 }^{ o  }$
$\theta ={ 60 }^{ o  }$
$h=6.6\times { 10 }^{ -34 }Js$
${ m } _{ e }=9.1\times { 10 }^{ -31 }kg$
$e=1.6\times { 10 }^{ -19 }c$
$n\lambda =2dsin\theta $
$\lambda =\dfrac { 2\times 1A\times sin{ 60 }^{ o  } }{ 1 } $
$\lambda =\sqrt { 3A } $
$\sqrt { V } =\dfrac { 1.27\times { 10 }^{ -10 } }{ \sqrt { 3 } \times { 10 }^{ -10 } } =50.18volts$

Multiple choice maths ellipse normal to an ellipse tangent and normal to an ellipse two dimensional analytical geometry-ii

A ray emanating from the point $(4, 0)$ is incident on the ellipse $9x^2\, +\, 25y^2\, =\, 225$ at the point $P$ with abscissa $3$. Find the equation of the reflected ray after first reflection.

  1. $12x + 5y = 48$
  2. $12x - 5y = 48$
  3. $-12x - 35y = 48$
  4. $-12x + 35y = 48$
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation

Solution:

Given equation of ellipse: $9x^2+25y^2=225$
$\cfrac{x^2}{25}+\cfrac{y^2}{9}=1$
Let $P(3,y _1)$
or, $9\times3^2+25y _1^2=225$
or, $25y _1^2=144$
or, $y _1=\pm\cfrac{12}{5}$
$\cfrac{x^2}{25}+\cfrac{y^2}{9}=1$
$\cfrac{x^2}{5^2}+\cfrac{y^2}{3^2}=1$
or, $e^2=1-\cfrac{b^2}{a^2}$

or, $e^2=1-\cfrac{9}{25}=\cfrac{16}{25}$
or, $e=\cfrac{4}{5}$
$ae=5\times\cfrac45=4$
It means the given point $(4,0)$ is focus of the ellipse.
We know that rays emanating from the one focus passes through other focus i.e $(-4,0)$
So, Equation of reflected ray $\Rightarrow y=\cfrac{\cfrac{12}{5}-0}{3+4}(x+4)$
or, $35y=12x+48$
or, $-12x+35y=48$
and another equation of reflected ray$\Rightarrow y=\cfrac{\cfrac{-12}{5}-0}{3+4}(x+4)$
or, $35y=-12x-48$
or, $-12x-35y=48$

Multiple choice chemistry mix and separate different types of mixtures homogenous and heterogenous mixtures all about mixtures

Particles of true solution are visible to naked eye.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Property True Solution Colloidal Solutions Suspension
Size of the particles < 1nm 1 1000nm >1000nm
Nature Homogeneous Heterogeneous Heterogeneous
Filterability Diffusion through parchment paper Particles of true Solution diffuse rapidly through filter paper as well as parchment paper. Colloidal particles pass through filter paper but not through parchment paper. Suspension particles do not pass through filter paper and parchment paper.
Visibility Particles of True Solution are not visible to naked eye. Colloidal particles are not seen to naked eye but can be studied through ultra microscope. Suspension particles are big enough to be seen by naked eye.
Tyndall effect True Solution does not show Tyndall effect. Colloids shows Tyndall effect. Suspension may or may not show Tyndall effect.
Appearance Transparent Translucent Opaque
Multiple choice physics refraction of light the nature of light speed of light and optical density introduction to light

Blue light of wavelength $480\ nanometers$, is most strongly reflected off a thin film of oil on a glass slide, when viewed near normal incidence. Assuming that the index of refraction of the oil is $1.2$ and that of the glass is $1.6$, what is the minimum thickness of the oil film (other than zero)?

  1. $150\ nm$
  2. $200\ nm$
  3. $300\ nm$
  4. $400\ nm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For constructive interference in a thin film (n_oil=1.2, n_glass=1.6, n_air=1.0), there is a phase shift at both surfaces. The condition for constructive interference is 2nt = m * lambda. For minimum thickness, m=1: 2 * 1.2 * t = 480 nm. t = 480 / 2.4 = 200 nm.

Multiple choice physics refraction of light the nature of light speed of light and optical density introduction to light

When light is refracted into a denser medium,

  1. its wavelength and frequency both increase

  2. its wavelength increases but frequency remains unchanged

  3. its wavelength decreases but frequency remains unchanged

  4. its wavelength and frequency both decrease
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$ _1\mu _2 = \dfrac{v _1}{v _2} = \dfrac{v _{rarer}}{v _{denser}} \Rightarrow v _1 > v _2$


$\Rightarrow v _1 > v _2$


$\Rightarrow \lambda _1 f _1 > \lambda _2 f _2$
Where $f$ is the frequency

when light goes from any rarer to any denser medium frequency remain unchanged.

$\therefore f _1 = f _2 = f$

$\Rightarrow \lambda _1 > \lambda _2$

hence wavelength decreases but frequency remains unchanged. 

Option C is correct.

Multiple choice physics refraction of light the nature of light speed of light and optical density introduction to light

Mark the correct statements (s) for a very thin soap film (RI = 1.33) whose thickness is much less then wavelength of visible light.

  1. Film appears dark.

  2. Film appears shiny.

  3. Film on glass (RI = 1.5) appears dark.

  4. Film on glass (RI = 1.5) appears shiny.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a very thin film (t << lambda), the path difference is negligible. The phase change occurs at the reflection from the glass interface (n=1.5 > n=1.33), leading to destructive interference, making it appear dark.