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

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

Read the following statements carefully
(A) Black body radiation is white
(B) Emissivity of a body is equal to its absorptive power
Mark correct option:

  1. Statement (A) is correct

  2. Statement (B) is correct

  3. Both are correct

  4. Both are wrong
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • (A) The combination of radiation of all the visible wavelengths makes white light. Hence black  body radiation is white

(B) Emissivity of body is equal to it's absorptive power, it is not less then absorptive power or greater than absorptive power
  • Hence both the statements are true
  • Hence option C is the right answer
           

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

Radiation coming from the hole of a Ferry's Black body is called 

  1. black radiation.

  2. cavity radiation.

  3. Ferry's radiation.

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
$\rightarrow$ Radiation coming from the hole of ferry's black body is called cavity radiation because this black body is double walled evacuated spherical cavity whose inner wall is blackened

Multiple choice physics observing space: telescopes space research and satellites space travel space exploration and forms of light

First adjustment of a spectrometer is :

  1. focusing the distant object

  2. focusing the cross wires

  3. focusing the slit

  4. focusing near objects
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

First we look through the telescope at any light - coloured surface and push the eyepiece in and out until we can see the cross-wires sharply, without straining our eyes, So, first adjustment in a spectrometer is focusing of the cross wires.

Multiple choice physics measurements and experimentation vernier calliper and screw gauge least count of vernier calliper and screw gauge measurement of length

In an experiment, the value of refractive index of a plastic has been found 1.33,1.30, 1.34 and 1.29 in successive measurements. Find the mean absolute error for refractive index.  

  1. $0.12$
  2. $0.02$
  3. $0.10$
  4. $0.01$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Here the mean value, $\bar{n}=\dfrac{1.33+1.30+1.34+1.29}{4}=1.31$
The absolute error in each measurements are, 
$\Delta n _1=\bar{n}-n _1=1.31-1.33=-0.02$;
$\Delta n _2=\bar{n}-n _2=1.31-1.30=0.01$;
$\Delta n _3=\bar{n}-n _3=1.31-1.34=-0.03$;
$\Delta n _4=\bar{n}-n _4=1.31-1.29=0.02$;
The mean absolute error, $\Delta \bar{n}=\dfrac{|\Delta n _1|+|\Delta n _2|+|\Delta n _3|+|\Delta n _4|}{4}=\dfrac{0.02+0.01+0.03+0.02}{4}=0.02$

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 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.