CBSE · Class 10 · Science · Chapter 11

Human Eye and the
Colourful World

Complete chapter resources for CBSE Class 10 Science — topic breakdown, key concepts, sample questions, previous year board questions, and instant AI question paper generation.

4Topics
5–7Board marks
8Sample questions
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Key Concepts — Chapter 11
  • Power of accommodation: Ability of eye lens to change focal length
  • Near point (normal eye): 25 cm (least distance of distinct vision)
  • Myopia correction: Concave (diverging) lens
  • Hypermetropia correction: Convex (converging) lens
  • Dispersion: White light → VIBGYOR via prism (n ∝ 1/λ)
  • Scattering: I ∝ 1/λ⁴ (Rayleigh's law)
Chapter Overview

What this chapter covers

Chapter 11 begins with the structure and functioning of the human eye — the cornea, iris, pupil, lens, ciliary muscles, and retina. The power of accommodation is the central concept: ciliary muscles adjust the curvature of the eye lens to focus on objects at different distances, from the near point (25 cm) to infinity (far point). When this mechanism fails, defects of vision arise — myopia (near-sightedness) and hypermetropia (far-sightedness), each corrected by an appropriate lens, plus presbyopia (age-related loss of accommodation) and astigmatism.

The second half of the chapter explores refraction of light through a glass prism, leading to dispersion — the splitting of white light into its constituent colours (VIBGYOR). The refractive index of glass varies with wavelength, so each colour bends by a different angle. This explains the rainbow: sunlight dispersed by water droplets after internal reflection creates the coloured arc. The chapter also covers atmospheric refraction, which causes the apparent position of stars to shift and makes the sun visible just after sunset.

The final topic is scattering of light. Rayleigh's law states that shorter wavelengths scatter far more intensely (scattering ∝ 1/λ⁴), which is why the sky appears blue and the sun appears red at sunrise and sunset. The danger signals on roads and railways use red light because it has the longest wavelength and scatters least, ensuring maximum visibility through fog and haze.

Topics

What's inside Chapter 11

As per NCERT Class 10 Science (CBSE syllabus)

Topic 1
The Human Eye
Structure of the eye: cornea, iris, pupil, crystalline lens, ciliary muscles, retina, optic nerve. Function of each part. Power of accommodation and the near and far points of a normal human eye.
Topic 2
Defects of Vision and their Correction
Myopia (concave lens correction), hypermetropia (convex lens correction), presbyopia (bifocal lens), and astigmatism. Cause of each defect — eyeball shape or ciliary muscle weakness — and the corrective lens power required.
Topic 3
Refraction of Light through a Prism & Dispersion
Angle of deviation, angle of prism, dispersion of white light into VIBGYOR. Recombination of spectrum by an inverted prism. Formation of a rainbow — primary and secondary. Atmospheric refraction: twinkling of stars, early sunrise and late sunset.
Topic 4
Scattering of Light
Rayleigh scattering: intensity ∝ 1/λ⁴. Why the sky is blue, why the sun appears red at sunrise/sunset, why danger signals are red. Tyndall effect — scattering by colloidal particles (e.g. smoke, fog, milk).
Connections

How this chapter fits in

Useful for setting question difficulty and cross-chapter papers.

Builds on
Ch 10 · Light — Reflection & Refraction
Laws of refraction, refractive index, lens formula and power
Class 9 · Natural Phenomena
Reflection of light, mirrors, and basic optics concepts
Chapter 11 Human Eye &
Colourful World
Leads to
Class 11 · Wave Optics
Interference, diffraction, polarisation, and Huygens' principle
Class 12 · Ray Optics & Optical Instruments
Microscopes, telescopes, resolving power, and aberrations
Board Blueprint

Marks & question-type breakdown

Typical pattern based on CBSE Class 10 Science board papers from the last five years.

Question type Marks Typical count What's usually tested
MCQ / Objective 1 1–2 Defect of vision identification, type of corrective lens, or scattering law
Very Short Answer 2 1 Why sky is blue / sun appears red; near point and far point definitions
Short Answer 3 1 Dispersion through prism, rainbow formation, or defect + correction with diagram
Long Answer / Diagram-based 5 0–1 Detailed eye structure diagram, comparison of defects, atmospheric refraction explanation
Total (approximate) 5–7 3–4 Weightage varies across paper sets and years
Sample Questions

8 sample questions — generated by MarksZen AI

Aligned to CBSE Class 10 Science Chapter 11. Covers all question types across Easy, Medium, and Hard difficulty.

Q1 Easy 1 mark MCQ
Which type of lens is used to correct myopia? (a) Convex lens (b) Concave lens (c) Bifocal lens (d) Cylindrical lens
Q2 Easy 2 marks Short Answer
What is the least distance of distinct vision for a normal human eye? Why can the eye not see objects placed closer than this distance clearly?
Q3 Medium 2 marks Short Answer
Why does the sky appear blue during the day but the sun appears reddish at sunrise and sunset? Explain in terms of scattering of light.
Q4 Medium 3 marks Short Answer
A person cannot read a newspaper clearly when held closer than 50 cm from the eyes. Name the defect of vision. What type of lens is needed to correct it? With the help of a ray diagram, show how the defect is corrected.
Q5 Medium 3 marks Short Answer
Draw a labelled diagram to show the dispersion of white light through a glass prism. Name the colours of the spectrum in order from the least deviated to the most deviated.
Q6 Hard 4 marks Word Problem
A student suffers from myopia and cannot see objects clearly beyond 2 m. Calculate the power of the corrective lens required. Also state the type of lens and explain the image formation before and after correction with the help of ray diagrams.
Q7 Hard 5 marks Long Answer
With a neat labelled diagram, describe the structure and working of the human eye. Explain the role of the ciliary muscles and the iris. What is the power of accommodation, and how does it decrease with age?
Q8 Hard 5 marks Case-Based
Read the following and answer the questions: Riya observes that the stars appear to twinkle on clear nights but the planets do not. Her grandfather tells her that this is due to atmospheric refraction. (i) Why do stars appear to twinkle? (ii) Why don't planets twinkle like stars? (iii) Why does the sun appear about 2 minutes before actual sunrise? (iv) What is atmospheric refraction?
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Previous Year Questions

From CBSE board examinations

Actual questions from past Class 10 Science board papers — Human Eye and the Colourful World chapter.

Board 20223 marks
A person needs a lens of power −4.5 D for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 D. What is the focal length of the lens required for correcting (i) distant vision and (ii) near vision? (CBSE All India 2022)
Board 20233 marks
Explain with a ray diagram: (a) the formation of a rainbow, and (b) why the sky appears blue. (CBSE Delhi 2023)
Board 20205 marks
Draw a neat labelled diagram of the human eye. What is the power of accommodation of the eye? Explain with diagrams the two common defects of vision — myopia and hypermetropia — and how they are corrected. (CBSE 2020)
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FAQ

Questions teachers ask

How many marks does Human Eye and the Colourful World carry in the CBSE Class 10 board exam? +
This chapter typically carries 5–7 marks in the CBSE Class 10 Science board exam, spread across 2–3 questions. Expect one 1-mark MCQ on the power of accommodation or defects of vision, one 2-mark short answer on refraction phenomena, and one 3-mark question on dispersion or atmospheric optics. The chapter has been consistently present in board papers for many years.
What is the power of accommodation of the human eye? +
Power of accommodation is the ability of the eye lens to adjust its focal length by changing its curvature, enabling the eye to see objects at varying distances clearly. The ciliary muscles control this adjustment. The normal human eye has a far point at infinity and a near point at about 25 cm (least distance of distinct vision). As age increases, the power of accommodation decreases, leading to presbyopia.
What is the difference between myopia and hypermetropia, and how are they corrected? +
Myopia (short-sightedness) is the inability to see distant objects clearly; the image forms in front of the retina due to an elongated eyeball or over-curved lens. It is corrected by a concave (diverging) lens. Hypermetropia (long-sightedness) is the inability to see nearby objects clearly; the image forms behind the retina. It is corrected by a convex (converging) lens. Both questions appear frequently as 2–3 mark questions in board exams.
Why does the sky appear blue and the sun appear red at sunrise and sunset? +
The blue colour of the sky is due to Rayleigh scattering — shorter wavelength blue light is scattered much more strongly by atmospheric gas molecules than longer wavelength red light, so we see blue from all directions. At sunrise and sunset, sunlight travels through a much longer path of atmosphere, and almost all blue light is scattered away, leaving predominantly red and orange wavelengths to reach the observer, making the sun appear reddish.
How do I generate a custom question paper for Human Eye and the Colourful World using MarksZen? +
Sign up for a free MarksZen account, choose CBSE Class 10 Science, select Chapter 11 (Human Eye and the Colourful World), set your preferred question-type mix and total marks — the AI generates a complete board-aligned paper with answer key in under 2 minutes, ready for PDF export.