Human Eye and the Colourful World

Structure of the Human Eye

• Eye Ball: Spherical, 2.3 cm diameter
• Cornea: Transparent, main refraction
• Lens: Convex, focal length adjustments
• Iris: Controls pupil size, colored part
• Retina: Image formation screen

Image Formation

• Light enters through cornea
• Image: Real, diminished, inverted
• Rods and cones: Light-sensitive cells
• Electric signals sent to brain

Accommodation

• Near objects: Ciliary muscles contract
• Distant objects: Ciliary muscles relax
• Focal length changes for clarity

Range of Normal Vision

• Near point: 25 cm
• Far point: Infinity
• Persistence of vision: 1/16 second

Defects of Vision

• Myopia: Near-sightedness, image before retina
• Hypermetropia: Far-sightedness, image behind retina
• Presbyopia: Weak accommodation, both defects
• Cataract: Cloudy lens, surgery needed

Refraction of Light

• Prism: Transparent medium, angle of prism
• Angle of deviation: Between incident and emergent rays
• Dispersion: Splitting of white light

Atmospheric Phenomena

• Twinkling of stars: Atmospheric refraction
• Rainbow: Dispersion by water droplets
• Advance sunrise: Refraction raises sun

Scattering of Light

• Tyndall effect: Visible light path
• Blue sky: Shorter wavelengths scattered
• Cloud appearance: Size of particles