Tag: physics

Questions Related to physics

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. $10^{-8}\ m$

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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

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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. $6^0 4'$

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Correct Option: A

Fill in the blanks:

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

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

  1. diffraction

  2. scattering

  3. dispersion

  4. refraction

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Correct Option: C
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.

State whether the following statement is True or False. 

You can see a rainbow only when your back is towards the sun

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

  1. True

  2. False

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Correct Option: A
Explanation:

A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky.

Now I won't get scientific, but apply your logic here.

Light which is reflected comes from the sun. So, rainbow is basically reflecting the light of the sun back. So think, how can you reflect something by staying at the same side as of the object you want to reflect?

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

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

  1. True

  2. False

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Correct Option: B
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 $False$.

Dispersion of white light into its constituent colours occurs during 

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

  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

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Correct Option: D
Explanation:

Upon entry of white light at the first boundary of a triangular prism, there will be a slight separation of the white light into the component colours of the spectrum. Upon exiting the triangular prism at the second boundary, the separation becomes even greater and ROYGBIV is observed in its splendor. Hence, Dispersion of white light into its constituent colours occurs during refraction at the boundary of a transparent medium.

Dispersion of white light into its constituent colours occurs during

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

  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.

Show answer
Correct Option: D
Explanation:

Upon entry of white light at the first boundary of a triangular prism, there will be a slight separation of the white light into the component colours of the spectrum. Upon exiting the triangular prism at the second boundary, the separation becomes even greater and ROYGBIV is observed in its splendor. Hence, Dispersion of white light into its constituent colours occurs during refraction at the boundary of a transparent medium.

Line spectrum is obtained from the :

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

  1. Sun

  2. Filament of the bulb

  3. Mercury lamp

  4. Burning coal

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Correct Option: C
Explanation:

As a light source, we will use a mercury lamp, which emits light at several discrete wavelengths. The device we are using is called a prism spectrometer because, once the prism is calibrated, it can be used to measure the wavelengths of the lines in the spectra produced by various atoms.

A piece of cloth looks red in sun light. If it is held in the blue portion of a solar spectrum, it will appear

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

  1. Red

  2. Black

  3. Blue

  4. White

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Correct Option: B
Explanation:

A cloth piece looks red in sun light because it absorbs all the colours of sun light except red, red is reflected to our eyes.

When red cloth piece is held in only the  blue portion of solar spectrum, the blue light will be absorbed by red cloth and as there is no red light is to reflect, therefore no colour will be reflected back i.e. cloth piece will appear black.