Human Eye
Physics · मानव नेत्र · 22 facts
Eye works like camera; cornea+lens focus light on retina
Cornea: outermost transparent layer; max refraction here
Iris controls pupil size to regulate light entry
Pupil: dilates in dark, contracts in bright light
Crystalline lens: biconvex; changes shape for focusing (accommodation)
Retina: rods (dim light vision) and cones (colour vision)
Optic nerve carries signals from retina to brain
Blind spot: optic nerve exit point; no vision here
Near point = 25 cm for normal eye; Far point = infinity
Myopia: image before retina; concave lens corrects
Hypermetropia: image behind retina; convex lens corrects
Presbyopia: old-age; loss of accommodation; bifocal lens
Astigmatism: uneven cornea; cylindrical lens corrects
Colour blindness: genetic; more in males
Persistence of vision: 1/16th second; basis of movies
Rainbow: dispersion+reflection+refraction in water drops
Atmospheric refraction: star twinkling, early sunrise, delayed sunset
Sky blue: Rayleigh scattering (shorter wavelength scattered more)
Sun red at sunrise/sunset: blue scattered, red reaches us
Danger signals red: least scattering, travels farthest
VIBGYOR: Violet to Red (increasing wavelength, decreasing frequency)
Total colours in visible spectrum: 7 (VIBGYOR)