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प्रश्न
A prism causes dispersion of white light while a rectangular glass block does not. Explain.
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उत्तर
In a prism, the refraction of light takes place at the two slant surfaces. The dispersion of white light occurs at the first surface of the prism where its constituent colours have deviated through different angles. At the second surface, these split colours suffer the only refraction and they get further separated. But in a rectangular glass block, the refraction of light takes place at the two parallel surfaces. At the first surface, although the white light splits into its constituent colours on refraction, these split colours on suffering refraction at the second surface emerge out in form of a parallel beam, which gives an impression of white light.
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संबंधित प्रश्न
Name three factors on which the deviation produced by a prism depends and state how does it depend on the factors stated by you.
How does the deviation produced by a triangular prism depend on the colours (or wavelengths) of light incident on it?
Which colour of white light travels fastest in glass?
In following diagram shows a thin beam of white light from a source S striking on one face of a prism.
What conclusion do you draw from the observation in part (b) above?
(i) Draw a diagram to show the splitting of white light by a prism into its constituent colour.
(ii) Draw another diagram to show how the colours of spectrum of white light can be combined
to give the effect of white light.
Write the approximate wavelengths for blue.
Fig shows part of the arrangement for obtaining pure spectrum.
(a) Complete thediagram and show how to obtain a pure spectrum.
(b) What are the conditions necessary for obtaining a pure spectrum?
Give a reason, why the violet colour of white light deviated most and red colour of white light deviated least.
Draw a neat diagram to show the arrangement you would use to project a pure spectrum of white light on a screen.
