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What is a rainbow? Draw a… (Class 10 Science 2025, Q31)

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ScienceCBSE Class 10 · Board exam 2025, set 31/3/1 · 3 marks · Short answer

CBSE Class 10 Science 2025: question 31

Set in the CBSE Class 10 board exam of 2025, paper 31/3/1, section C, question 31, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q31 · 3 marks · Short answerThe Human Eye and the Colourful World

What is a rainbow? Draw a labelled diagram to show its formation.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/3/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Each raindrop acts like a small prism.

Hint 2

Light is refracted, reflected inside, and refracted again.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. A rainbow is a natural spectrum of seven colours appearing in the sky after a rain shower, seen in the direction opposite to the sun. It is caused by dispersion of sunlight by tiny water droplets in the atmosphere.

    1 mark

  2. Diagram: draw a spherical raindrop with sunlight (white light) entering it. At entry the light is refracted and dispersed into colours; the rays then undergo internal reflection at the back surface of the drop, and refract again on leaving the drop. Show red and violet separating, with the observer's eye on the side of the incoming sunlight (sun behind observer).

    1½ marks

  3. Label: sunlight, raindrop, refraction and dispersion, internal reflection, refraction, red, violet; mark arrows on all rays.

    ½ mark

Answer: A rainbow is a natural spectrum after rain due to dispersion, refraction and internal reflection of sunlight by water droplets; labelled diagram of a raindrop.

Where the marks are

  • Definition of rainbow (1 mark)
  • Diagram of raindrop showing refraction, dispersion, internal reflection and refraction (1½ marks)
  • Labels and arrows on rays (½ mark; ½ deducted if arrows missing)

Revise the chapter

Practise this chapterBoard-style questions from The Human Eye and the Colourful World, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/3/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.