Tag: spectra

Questions Related to spectra

Which of the following are Primary pigments ?

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

  1. Yellow, green, magenta

  2. Magenta, yellow, cyan

  3. Blue, green, yellow

  4. Blue, green, violet

Show answer
Correct Option: B
Explanation:

The primary colors of pigment are used when producing colors from reflected light; for example, when mixing paint or using a color printer. The primary colors of pigment are Magenta, Yellow, and Cyan. 

Hence, the correct answer is OPTION B.

Which of the following are Primary colors ?

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

  1. Red, blue, yellow

  2. Red, orange, yellow

  3. Red, blue, green

  4. Red, green, cyan

Show answer
Correct Option: A
Explanation:
The primary colors are those which cannot be created by mixing other colors in a given color space. The primary colors are Red, Blue and Yellow.

Hence, the correct answer is OPTION A.

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

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

  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

Show answer
Correct Option: B
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.

Dispersion of light is caused due to :

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

  1. intensity of light

  2. density of medium

  3. wavelength

  4. none of the above

Show answer
Correct Option: C
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.

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

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

  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

Show answer
Correct Option: C

The phenomenon of dispersion arises because of

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

  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

Show answer
Correct Option: C

Soap bubble appears coloured due to the phenomenon of:-

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

  1. Total internal feflection

  2. Interference by division of amplitude

  3. Interference by division of wavefront

  4. Diffraction of light

Show answer
Correct Option: C
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.

Oil floating on water looks coloured due to interference of light. What should be the order of magnitude of the thickness of oil layer in order that this effect may be observed?

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

  1. $10^{-6}\ m$

  2. $10^{-2}\ m$

  3. $10^{-10}\ m$

  4. $10^{-8}\ m$

Show answer
Correct Option: A

Dispersion of ......... colour is minimum in visible range of light.

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

  1. Red

  2. Blue

  3. Green

  4. Violet

Show answer
Correct Option: A

Calculate the angle of dispersion between red and violet colours produced by a flint glass prism of refracting angle of $60^0$. Given : $\mu _v = 1.663$ and $\mu _r = 1.622$.

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

  1. $4^0 6'$

  2. $5^0 6'$

  3. $3^0 4'$

  4. $6^0 4'$

Show answer
Correct Option: A