← 🫀 Human body · usually met in Std 6-10
A lens that throws an upside-down image onto a light-sensitive screen, and a brain that makes sense of what arrives.
Light enters through the cornea, passes the pupil — whose size the iris controls — and is focused by the lens onto the retina at the back. The retina's rods see in dim light but not in colour; the cones see colour and detail and need good light. The image formed there is inverted and small, and the brain turns it the right way up, which it learned to do in infancy.
The lens changes shape to focus at different distances, and when that adjustment falls short the result is short or long sight, corrected by spectacles. The retina has one spot with no receptors at all, where the optic nerve leaves — the blind spot. You never notice it because the brain fills the gap, which is worth remembering whenever you are sure you saw something clearly.
Want to see it moving? Search YouTube for “The eye” ↗ — we send you to the search rather than to one video, because a link to one video eventually rots.
This entry was written for Star Student in our own words — it is a summary, not a source. Here is where the people who actually hold these facts keep them. Go and check.
Your own textbook ↗Balbharati publishes the textbooks free to read online. Your chapter is the thing to check first — an encyclopedia is a summary, and the syllabus is the syllabus. World Health Organization ↗Health facts stated carefully, and updated when the evidence changes.Last gone through: 1 October 2026 · How these entries are written
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