Skip to content

With the help of a ray… (Class 10 Science 2026, Q34b)

questionbuddy.in/q/cbse-10-science-2026-31-3-1-q34b-help-ray-diagram-phenomenon-formation

ScienceCBSE Class 10 · Board exam 2026, set 31/3/1 · 2 marks · Very short answer

CBSE Class 10 Science 2026: question 34(b)

Set in the CBSE Class 10 board exam of 2026, paper 31/3/1, section C, question 34(b), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q34(b) · 2 marks · Very short answerThe Human Eye and the Colourful World

With the help of a ray diagram, explain any phenomenon of formation of spectrum in nature.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/3/1.

Hints

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

Hint 1

Think of a spectrum you can see in the sky after rain.

Hint 2

Each raindrop behaves like a tiny prism. What three things happen to sunlight inside it?

Hint 3

Trace a ray: refraction with dispersion on entry, internal reflection at the back, and refraction on exit.

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. Phenomenon: formation of a rainbow. A rainbow is a natural spectrum seen in the sky after a shower, always in the direction opposite to the Sun. Here the tiny water droplets in the atmosphere act like small prisms. Sunlight entering a droplet is refracted and dispersed into its colours. It then undergoes internal reflection at the back surface of the droplet. It is refracted again as it comes out, and the colours spread further apart so that they reach the observer's eye as a band from red to violet.

    1 mark

  2. Ray diagram (described):

    • Draw a circular raindrop with a ray of white sunlight entering its upper part. Mark refraction at entry, with the ray splitting into red and violet rays (dispersion).
    • Show both rays striking the back surface of the drop and undergoing internal reflection.
    • Show both rays refracting out of the lower front part of the drop towards the observer.
    • Label: sunlight, raindrop, refraction and dispersion, internal reflection, refraction, red, violet.
    1 mark

Answer: Rainbow: sunlight is refracted and dispersed, internally reflected and refracted again by raindrops (with a ray diagram of a raindrop).

Where the marks are

  • Labelled ray diagram of light through a raindrop showing dispersion, internal reflection and refraction (1 mark)
  • Explanation that raindrops disperse sunlight, reflect it internally and refract it again on emerging, forming a rainbow (1 mark)

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 paper2026 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.