Back to Science on Exam Trends
Human Eye & Colourful World
Medium trendapprox. 5 marksSections C/D — one defect-correction numerical plus reason-based questions on dispersion, scattering and atmospheric refraction.
CBSE 2027 — dates, rules and official papers →Ask the tutor1In correction numericals always state the lens type AND the sign of the power with its unit (concave = negative D, convex = positive D) — a bare magnitude without the sign or the dioptre unit loses marks.
Notesformulae · proofs · mind-map — one view
Learn the 6 conceptsteach yourself first, then practise each
Power of accommodation (ciliary muscles vary focal length; near point 25 cm, far point ∞)1–3 marks
Explain how a normal eye focuses near and distant objects on the retina.
Defects of vision and correction — myopia (concave, −P), hypermetropia (convex, +P), presbyopia3–5 marks Visual
Name the defect, pick the corrective lens and justify its sign of power.
Lens power P = 1/f (dioptre) for the corrective lens2–3 marks
Compute the lens needed once the required focal length is fixed.
Refraction through a prism and dispersion of white light (VIBGYOR spectrum)2–3 marks Visual
Explain the spectrum and angle of deviation on a prism diagram.
Atmospheric refraction (twinkling of stars, advance sunrise, delayed sunset)2–3 marks
Give the refraction-based cause for everyday sky phenomena.
Scattering of light (Tyndall effect, blue sky, red danger signals)2–3 marks
Use wavelength-dependent scattering to explain the sky's colour and why red signals carry far.
When you’re ready — practise or test the whole topic