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 physics oscillations and waves polarization of light polarisation of light polarisation

Two polaroids are kept crossed to each other. Now one of the polaroids is rotated through an angle $45^0$. The percentage of incident light now transmitted through the system is: 

  1. 15%

  2. 25%

  3. 50%

  4. 60%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Initially crossed (90 degrees), I=0. Rotating one by 45 degrees means the angle between them is 45 degrees. Intensity I = (I0/2) * cos^2(45) = I0/4 = 25%.

Multiple choice physics oscillations and waves polarization of light polarisation of light polarisation

A plane polarized light is incident normally on a tourmaline plate. Its $\vec { E } $ vectors make an angle of ${ 60 }^{ o }$ with the optic axis of the plate. Find the percentage difference between initial and final intensities.

  1. $25$%
  2. $50$%
  3. $75$%
  4. $90$%
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the initial intensity of the light be  $I _o$.
Final intensity of the light   $I = I _o\cos^2\theta$
where  $\theta= 60^o$
$\implies \ I = I _o\times \cos^260^o = 0.25 I _o$
Percentage change in the initial and final intensities  $ = \dfrac{I _o - I}{I _o}\times 100 = \dfrac{I _o-0.25I _o}{I _o}\times 100 = 75$ %
So option C is correct.

Multiple choice physics light, shadows and images substances which allow light to pass through and those which do not transparent, opaque and translucent objects shadows

Opaque objects:

  1. Allow the light to pass through them

  2. Do not let the light to pass through them

  3. Absorb some amount of light and let the remaining to pass through them

  4. Allows the light from natural sources and rejects if it is from artificial sources
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The majority of objects are opaque, which means you can't see through them. This is due to the fact that light can't pass through them. Examples of opaque objects include wood, gold, cement, metal, some types of coloured plastic, and so on.

Multiple choice detection and recording of x-ray images option c: imaging physics

Which of the following phenomenon supports the quantum nature of light?

  1. Compton effect

  2. Interference

  3. Diffraction

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

The wave nature of light is exhibited by interference, diffraction and polarisation of light.
Compton effect is the strongest evidence to show the particle nature of light, and hence the quantum theory of light.

So, the answer is (A).

Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

The velocity of light in glass whose refractive index w.r.t air is $1.5$ is $2 \times 10^8 \,m/s$. In a certain liquid, the velocity of light is found to be $2.5 \times 10^8 \,m/s$. The refractive index of the liquid w.r.t air is

  1. $0.8$
  2. $0.9$
  3. $1.2$
  4. $1.33$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Velocity of light in glass $(v _1)=2\times 10^8 m/s$
Refractive index of glass $(\eta _1)=1.5$
w.r.t air
Velocity of light in certain $2\times 10^8\ m/s$
liquid $(v _2)$
Let refractive index of certain $=\eta _g$
liquid w.r.t air
Using formula,
$Refractive\ index=\dfrac{Velocity\ of\ light}{Velocity\ of\ light\ in\ med}$
we get
$\dfrac{\eta _1}{\eta _2}=\dfrac{V _2}{V _1}$
$\eta _2=\dfrac{\eta _1 V _1}{V _2} $
$\eta _2=\dfrac{31.5\times 2\times 10^8}{52.5\times 10^8}$
$\eta _2=\dfrac{6}{5}=1.2$
$\therefore$ Refractive index of certain liquid$=1.2$
Multiple choice chemistry element, compound and chemical reaction materials around us materials around us and different types of houses matter and its states

The shining of the sun and stars is due to the __________ state of matter.

  1. plasma

  2. Bose-Einstein condensate

  3. solid

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

The shining of the sun and stars is due to the plasma state of matter. The plasma state causes ionization of the gases which causes shining of the substance.

Multiple choice physics superposition of waves coherence young's double slit experiment interference

To demonstrate the phenomenon of interference we require two sources which emit radiation of

  1. nearly the same frequency

  2. the same frequency

  3. different wavelength

  4. the same frequency and having a definite phase relationship
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For stable interference patterns, the two sources must be coherent, meaning they must have the same frequency and a constant phase relationship.

Multiple choice physics superposition of waves coherence young's double slit experiment interference

Which of the following is not an essential condition for interference?

  1. The two interfering waves must propagate in almost the same direction

  2. The waves must have the same period and wavelength

  3. The amplitudes of the two waves must be equal

  4. The two interfering beams of light must originate from the same source
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When two waves are propagate in same direction

Multiple choice physics superposition of waves coherence young's double slit experiment interference

Which of the following, cannot produce two coherent sources?

  1. Lloyd's mirror

  2. Fresnel biprism

  3. Young's double sit

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

Two coherent sources are produced in Lloyd's mirror by reflection of light from a plane mirror, hence the original source and its image acting as coherent sources.

In fresnel biprism, light from a point source gets refracted by a biprism to produce two coherent sources.
In Young's double slit, two coherent sources are produced by passing of light from a single source through two slits.

Multiple choice physics superposition of waves coherence young's double slit experiment interference

The device which produces highly coherent sources  is

  1. Fresnel biprism

  2. Young's double sit

  3. Laser

  4. Lloyd's mirror
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The atoms in the laser medium are pumped up energetically by an external power source, producing a population inversion of atomic energies. The pumped-up atoms can return to lower energy levels by emitting light at only certain frequencies, depending on the particular medium, which can be a solid (e.g. laser diode), a liquid (e.g. dye laser) or a gas (e.g. helium-neon laser).

We get temporal coherence because the excited atoms emit only at that preferred frequency.

Multiple choice physics superposition of waves coherence young's double slit experiment interference

Coherence is a measure of

  1. capability of producing interference by wave

  2. waves being diffracted

  3. waves being reflected

  4. waves being refracted
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Interference is a phenomenon in which two waves superpose to form a resultant wave of greater or lower amplitude.

If the sources are coherent, the interference pattern obtained is more ordered, with definite spacing between fringes. 
Thus coherence is a measure of capability of producing interference of wave.

Multiple choice physics superposition of waves coherence young's double slit experiment interference

The phenomenon of interference is shown by:

  1. longitudinal mechanical waves only

  2. electromagnetic waves only

  3. transverse mechanical waves only

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

All of the above type of waves.


Interference of a wave is the phenomenon that usually happens when the two waves reinforce,while travelling in the same medium. The interference of waves causes the medium to take on a shape that results from the net effects of the two individual waves simultaneously acting upon the particles of the medium.