Human Eye and Colorful World

Introduction

• Human Eye: Light-sensing organ, resolution ~576 megapixels.
• Comparison: iPhone 14 Pro Max camera resolution is 48 megapixels.

Structure and Functions of the Human Eye

Parts of the Human Eye

• Cornea: Transparent membrane, light entry point.
• Crystalline Lens: Soft, flexible, focuses images on the retina.
• Iris: Muscular diaphragm, controls pupil size.
• Pupil: Regulates light entry, adjusts to light intensity.
• Ciliary Muscles: Hold lens, change its shape.
• Retina: Light-sensitive, generates electrical signals.
• Optic Nerve: Transmits signals to the brain.
• Blind Spot: Where optic nerve connects to the eye.
• Aqueous Humor: Liquid between cornea and lens, keeps cornea moist.
• Vitreous Humor: Liquid between lens and retina, helps maintain shape.

Power of Accommodation

• Ability to adjust lens focal length.
• Viewing Distant Objects: Ciliary muscles relax, lens thins.
• Viewing Close Objects: Ciliary muscles contract, lens thickens.

Eye Functionality

Far and Near Points

• Far Point: Maximum clear vision distance (infinity for normal eye).
• Near Point: Minimum clear vision distance (25 cm for adults).

Cataract

• Lens becomes cloudy, causes vision loss.
• Corrected by cataract surgery.

Importance of Two Eyes

• Wider field of vision (180 degrees vs. 150 degrees for one eye).
• Better depth perception and faint object detection.

Defects of Human Eye

Types of Defective Vision

1. Myopia (Nearsightedness)

   • Clear near vision, blurry far vision.
   • Image falls in front of retina.
   • Corrected with concave lens.

2. Hypermetropia (Farsightedness)

   • Clear far vision, blurry near vision.
   • Image falls behind retina.
   • Corrected with convex lens.

3. Presbyopia

   • Difficulty focusing on nearby objects.
   • Due to weakening ciliary muscles and lens flexibility.
   • Corrected with bifocal lenses.

Refraction and Dispersion of Light

Refraction Through Prism

• Light deviates, creates angle of deviation.

Dispersion of White Light

• Splits into 7 colors: Violet, Indigo, Blue, Green, Yellow, Orange, Red.
• Spectrum of Sunlight: Created by dispersion.

Rainbow

• Natural spectrum by raindrops.
• Water droplets act as prisms causing refraction and dispersion.

Atmospheric Refraction

Effects

• Apparent Star Positions: Stars appear higher due to light bending.
• Twinkling Stars: Caused by atmospheric density variations.
• Planets Do Not Twinkle: Due to larger, steady light sources.

Sunrise and Sunset

• Advanced Sunrise/Delayed Sunset: Sun appears before actual horizon crossing due to refraction.

Scattering of Light

Tyndall Effect

• Light scattering by suspended particles.

Color of the Sky

• Blue Sky: Blue light scattered more due to shorter wavelengths.
• Red at Sunrise/Sunset: Red light scatters less, travels longer.

Significance of Red Light

• Danger Signals: Red is least scattered, visible at long distances.

This summary covers the human eye's structure and functions, defects, and concepts of light refraction and scattering in the atmosphere. The information is relevant in understanding vision and optical phenomena.