Directions: For question number 32, two statements are given, one labelled as Assertion (A) and the other is labelled as Reason (R). Select the correct answer from the codes given below. Assertion (A): When rays of white light pass through a prism, on emerging they give spectrum of seven colours. Reason (R): It is due to the scattering of light that red light bends minimum and violet light bends the maximum.
Directions: For question number 32, two statements are given, one labelled as Assertion (A) and the other is labelled as Reason (R). Select the correct answer from the codes given below. Assertion (A): When rays of white light pass through a prism, on emerging they give spectrum of seven colours. Reason (R): It is due to the scattering of light that red light bends minimum and violet light bends the maximum.
Options
C. Assertion (A) is true, but Reason (R) is false.
Hint
Check which physical phenomenon actually causes different colours to bend by different angles inside a prism — is it scattering, or refraction/dispersion?
Quick Oral Answer
The Assertion is true — a prism splits white light into a seven-colour spectrum. But the Reason is false in naming scattering as the cause; the correct cause is refraction/dispersion, where different colours travel at different speeds inside the glass and hence bend by different amounts.
Analysis & Explanation
Checking Assertion (A): The NCERT text (Section 10.4) states: "The prism has probably split the incident white light into a band of colours... The various colours seen are Violet, Indigo, Blue, Green, Yellow, Orange and Red... The splitting of light into its component colours is called dispersion." So Assertion (A) — that white light passing through a prism emerges as a spectrum of seven colours — is true.
Checking Reason (R): The text explains why this splitting happens: "Different colours of light bend through different angles with respect to the incident ray, as they pass through a prism. The red light bends the least while the violet the most." While the second part of R (red bends minimum, violet bends maximum) matches the text, R incorrectly attributes this bending to scattering. The chapter clearly separates two distinct phenomena: dispersion/refraction through a prism (Section 10.4), which causes the splitting of white light, and scattering of light by fine particles (Section 10.6, Tyndall effect), which is a completely different phenomenon responsible for effects like the blue colour of the sky. Bending of different colours in a prism is due to refraction (each colour has a slightly different refractive index/speed in glass, so each bends by a different amount), not scattering. Hence Reason (R), as worded, is false.
Why each option is right/wrong:
- (A) Incorrect — R is not simply an alternate true explanation; it wrongly names scattering as the cause.
- (B) Incorrect — R is false, not merely 'not the correct explanation'.
- (C) Correct — A is true; R is false because it misattributes the bending of colours to scattering instead of dispersion/refraction.
- (D) Incorrect — A is definitely true, as directly stated and explained in the chapter.
Common Mistakes
- 1Believing scattering (Tyndall effect / sky-blue phenomenon) is responsible for splitting of white light in a prism — that is actually caused by dispersion due to refraction, a different phenomenon covered later in the same chapter under 10.6.
- 2Marking option A because both statements individually 'sound correct', without checking that the Reason names the wrong physical process.
Interesting Facts
Isaac Newton confirmed that sunlight itself is made of seven colours by recombining the dispersed spectrum using a second, inverted prism, which produced white light again.
The acronym VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red) is used to remember the order of colours in the spectrum, with violet bending the most and red the least.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2026?
This question carries 1 mark in the CBSE Class 10 Science 2026 examination.
Which chapter does this question come from in Science?
This question is from the chapter "The Human Eye and the Colourful World" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Dispersion of White Light by a Glass Prism" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2026 paper?
This question appears in Section C in the CBSE Class 10 Science 2026 paper.