Class 10 Science Chapter 10 Human Eye and Colourful World Revision Notes

Class 10 Science Chapter 10 – The Human Eye and the Colourful World: Quick Revision Notes

• Power of accommodation: ability of the eye lens to adjust focal length via ciliary muscles
• Near point (normal eye) ≈ 25 cm; Far point (normal eye) = infinity
• Myopia (near-sightedness): distant objects blurred, far point < infinity → corrected with a concave (diverging) lens
• Hypermetropia (far-sightedness): near objects blurred, near point > 25 cm → corrected with a convex (converging) lens
• Presbyopia: age-related loss of accommodation → corrected with bifocal lenses
• Power of a lens: P = 1/f (f in metres); unit = dioptre (D)
• Concave lens → negative power; Convex lens → positive power
• Atmospheric refraction: bending of light due to continuously varying density of air
• Twinkling of stars: caused by atmospheric refraction of starlight through layers of varying density
• Planets do not twinkle: extended sources, twinkling effects of many points average out
• Advance sunrise / delayed sunset: each about 2 minutes, due to atmospheric refraction
• Tyndall effect: scattering of light by colloidal-sized particles
• Blue colour of sky: shorter wavelengths (blue/violet) scattered more by atmospheric molecules
• Reddish sun at sunrise/sunset: longer atmospheric path scatters away blue light, red light reaches the eye
• Sky appears black to astronauts: no atmosphere at high altitude to scatter sunlight

More on This Chapter

• NCERT Solutions – Chapter 10
• Extra Questions (HOTS) – Chapter 10
• Revision Notes – Chapter 10
• Class 10 Science Book (Catalog Page)

Quick visual: a worked diagram from the full Solutions page, for reference.

Last Updated: October 24, 2026

Common Mistakes Students Make in This Chapter

Frequently Asked Questions

What is the near point and far point of a normal human eye?
The near point (least distance of distinct vision) is about 25 cm, and the far point is at infinity for a normal eye — these two reference values are used throughout the chapter to define and diagnose vision defects.

Why does a rainbow form only when it is raining and the Sun is behind the observer?
A rainbow forms due to dispersion, refraction, and total internal reflection of sunlight inside tiny water droplets in the air; this specific combination of optical effects only happens when sunlight enters droplets at the correct angle, which requires the Sun to be behind the observer and water droplets in front.

What to Revise First (and Last) in This Chapter

Written by Satish

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