CBSE 2025 · Region 2 · Set 1 · Q39 · 4 marks
A person allowed a narrow beam of white light from the sun to enter a dark room through a small aperture and placed a glass prism in its path in such a manner that the beam falls on the face AB of the prism as shown in the figure.
A screen S is placed on the other side of the prism, facing AC. On turning the prism slowly, a beautiful band of colours is obtained on the screen. It is the spectrum of sunlight.(a)Name the phenomenon due to which a prism splits the incident white light into a band of colours.(b)State the reason of getting a band of seven colours in the above case.(c)Explain with the help of a labelled ray diagram, an experimental arrangement to show the recombination of the spectrum of white light.(ii)Draw a labelled ray diagram to show the formation of a rainbow.
A person allowed a narrow beam of white light from the sun to enter a dark room through a small aperture and placed a glass prism in its path in such a manner that the beam falls on the face AB of the prism as shown in the figure.
A screen S is placed on the other side of the prism, facing AC. On turning the prism slowly, a beautiful band of colours is obtained on the screen. It is the spectrum of sunlight.
(a)
Name the phenomenon due to which a prism splits the incident white light into a band of colours.
(b)
State the reason of getting a band of seven colours in the above case.
(c)
Explain with the help of a labelled ray diagram, an experimental arrangement to show the recombination of the spectrum of white light.
(ii)
Draw a labelled ray diagram to show the formation of a rainbow.
Marking-scheme solution
(a) Dispersion of light
(b) Different colours of light bend through different angles with respect to the incident ray as they pass through a prism.
(c) (i) Two identical prisms are placed in inverted position with respect to each other as shown. When spectrum produced by prism A is passed through the prism B, a beam of white light emerges from the other side of the prism B.
(c)
The Human Eye and the Colourful WorldDispersion of White Light by a Glass PrismUnderstandcase_studymedium
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CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.