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 spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

The phenomenon due to which white light splits into seven colours on passing through a prism is called _________

  1. reflection

  2. refraction

  3. dispersion

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

The phenomenon due to which white light splits into seven colours on passing through a prism is called dispersion. White light is made up of seven bands of colors each having different wavelengths. Upon passing through a medium, each of the colors travels at different speeds and hence has different angles of refraction leading to the splitting of the light i.e. dispersion.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

Dispersion of white light into its constituent colours occurs during :

  1. Reflection at a plane mirror

  2. Reflection at a concave mirror

  3. Internal reflection inside a spherical drop of water

  4. Refraction at the boundary of a transparent medium
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Answer is D.

The spectral colors of the rainbow are caused by dispersive refraction. Newton established that refraction causes the dispersion of light into its constituent colours. He named seven colors, in symmetry with the seven distinct notes in the Western musical scale.
Refraction is the bending of a light as it crosses the boundary into a different medium and it is determined by its refractive index, or how much the light is slowed down in the new medium.
Hence, dispersion of white light into its constituent colors occurs during refraction at the boundary of a transparent medium.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

The splitting of white light into several colours on passing through a glass prism is due to

  1. refraction

  2. reflection

  3. dispersion

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$ \bf{Refraction} $ of light is the phenomenon of bending of light or change in the direction of light, when it passes obliquely from one transparent medium to another.

$ \bf{Reflection} $ is the phenomenon in which light rays on striking a polished surface(such as a mirror) bounce back or are sent back into the same medium. 

$\bf{Dispersion} $ is the phenomenon of splitting of white light into its component colours (VIBGYOR) on passing through a glass prism.

Hence, the correct answer is OPTION C.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

The sky appears blue due to:

  1. reflection of light

  2. dispersion and scattering of light

  3. total internal reflection of light

  4. blue colour of water droplets
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The sky appears blue due to dispersion and scattering of white light from the Sun and the blue color scatters the most because of its small wavelength as compared to other colors in spectrum.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

The splitting of white light into its colored components is called _____.

  1. Spectrum

  2. Dispersion

  3. Deviation

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

The prism splits the incident light beam into a band of 7 colors. This band of colored components of a light beam is called its spectrum and the phenomenon of splitting of light into its component colours is called dispersion.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

When white light passes through a dispersive medium, it breaks up into various colours. Which of the following is true?

  1. Velocity of light for violet is greater than the velocity of light for red colour

  2. Velocity of light for violet is less than the velocity of light for red

  3. Velocity of light is the same for all colours

  4. Velocity of light for different colours
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When light falls on the glass prism, refraction takes place. Since the wavelength of different components of light is different and the frequency is constant, each component gets deviated by a different angle due to the difference in velocity in the glass medium. The red color having the maximum wavelength and velocity, deviates the least and forms the upper part of the spectrum whereas violet having the least wavelength and velocity deviates the most.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

Why do we study the Dispersion phenomenon using a glass prism and not a glass slab ?

  1. Light doesn't undergo any deviation inside a glass slab; so cannot be used to study Disprsion

  2. All of the dispersion that takes place at the first interface is exactly reversed at the second parallel surface, 'undoing' the effect of the first interface.

  3. Dispersion occurs only in prism and not in glass slab

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The Dispersion phenomenon using a glass prism and not a glass slab because when light passed through glass slab, it encounters TWO interfaces--one entering and the other leaving. All of the bending (and dispersion) that takes place at the first interfaces is exactly reversed at the second, 'undoing' the effect of the first interface; so although the emerging ray of light is displaced slightly from the entering ray, it travels in the same direction as the incoming ray and all wavelengths that separated at the first interface are re-combined. 
And in case of prism the second interface is NOT parallel to the first, the effects of the first interface are NOT reversed and the colors separated at that interface continue along different paths upon leaving the prism.
Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

Dispersion of light is caused due to :

  1. intensity of light

  2. density of medium

  3. wavelength

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The splitting of white light into its constituent colour is called dispersion of light. In this phenomenon, different colours contained in white emerge from the glass prism in different directions due to their different wavelengths.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

A ray of light containing both red and blue colours is incident on the refracting surface of a prism. Then,

  1. both colours suffer equal deviation

  2. red colour suffers more deviation

  3. red colour suffers less deviation

  4. deviation depends on the angle of prism
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Cauchy's dispersion formula, the refractive index is higher for shorter wavelengths (blue) than for longer wavelengths (red). Consequently, blue light deviates more than red light when passing through a prism.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

The phenomenon of dispersion arises because of

  1. The decomposition of a white light beam by a prism

  2. The refraction of light

  3. The refractive index of the prism material being different for different wave length

  4. The corpuscular nature of light
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dispersion occurs because the refractive index of the prism material varies with the wavelength of light. This causes different wavelengths to travel at different speeds and refract at different angles.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

Soap bubble appears coloured due to the phenomenon of:-

  1. Total internal feflection

  2. Interference by division of amplitude

  3. Interference by division of wavefront

  4. Diffraction of light
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
It is due to the interference of light. As the position of eyes is changed, path difference corresponding to different wavelength of the light emitted by the bubble change. Thus the intensities of different wavelengths are different resulting the bubble to be appeared colored. 
Option $-C$ is correct.
Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

Fill in the blanks:

The phenomenon of splitting of light into its component colours is ____________

  1. diffraction

  2. scattering

  3. dispersion

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

Colours are often observed as light passes through a triangular prism. Upon passage through the prism, the white light is separated into its component colours - red, orange, yellow, green, blue and violet. The separation of visible light into its different colors is known as dispersion.

Multiple choice physics spectra sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

When white light splits in seven colours, the phenomenon is called spectrum. 

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The phenomenon of splitting of white light into seven constituent colors is known as dispersion.

                           And, the band of seven colours obtained on the screen is known as spectrum.

Given statement is $False$.