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)

Written by Satish

NCERTBooks.org is an independent educational resource run by a small team focused on making official NCERT textbooks easy to find, read, and download for students, parents, and teachers across India. We are not affiliated with NCERT or the Ministry of Education -- we organise publicly available NCERT content by class and subject, verify links against official sources, and build tools (like our in-browser reader) that make studying more convenient. Every guide we publish is written and reviewed by our team based on the actual NCERT curriculum and syllabus.