Visible light

Visible light

1. ELECTROMAGNETIC SPECTRUM

   • Visible Light: 400–700 nm (ROYGBIV colors).
   • Radio Waves 1 mm – 100 km AM/FM radio, MRI scans
   • Microwaves 1 mm – 1 m Cooking, radar systems
   • Infrared 700 nm – 1 mm Thermal imaging, remote controls
   • Ultraviolet 10–400 nm Sterilization, black lights
   • X-rays 0.01–10 nm Medical imaging, security scans
   • Gamma Rays < 0.01 nm Cancer treatment

2. WAVE PROPERTIES

   • Core Concepts
     • Wavelength Distance between two wave peaks. Violet light: ~400 nm (short λ) | Red light: ~700 nm (long λ). Rainbow spectrum showing λ progression from violet (left) to red (right). Related: Radio waves (long λ, meters) vs. X-rays (short λ, nanometers).
     • Frequency (f): Waves per second (Hz). Violet: ~750 THz | Red: ~430 THz. Guitar string analogy: High-frequency vibration = high-pitched sound (like violet light’s high f). Related: Ultraviolet (higher f than violet) | Infrared (lower f than red).
     • Amplitude: Wave height = brightness/loudness. Dimmer switch: Lower amplitude = dimmer light. Light bulb: High A (bright) vs. low A (glow). Related: Sound: Amplitude = volume (shout vs. whisper).
     • Speed (c): v = λ × f (constant in a medium). In vacuum: ~300,000 km/s (slower in glass/water). Lightning vs. thunder: Light (fast) arrives before sound (slow). Related: Sound speed: Faster in solids than air.
     • Equation Highlight: E = h × f (Photon energy, where h = Planck’s constant) E=h×f(Photon energy, where h=Planck’s constant)

3. WAVE BEHAVIOR

   • Key Phenomena
     • Reflection: Light bounces off surfaces. Mirrors, polished metals
     • Refraction: Light bends when changing mediums. Prisms (rainbows), eyeglass lenses
     • Diffraction: Light spreads around obstacles. Color patterns on CDs/DVDs
     • Interference: Waves combineto reinforce/cancel. Soap bubble iridescence

4. APPLICATIONS

   • Visible Light:
     • Vision: Human eye detects 400–700 nm. Technology: Fiber optics (high-speed internet). Photography (lenses, filters).
   • Other EM Waves:
     • Medical: X-rays (bone fractures), UV (germicidal lamps). Communication: Radio (Wi-Fi, Bluetooth), microwaves (satellites). Energy: Solar panels (convert sunlight to electricity).
   • Real-World Connection:
     • Why microwaves heat food but visible light doesn’t? Microwaves match water molecules’ resonant frequency.

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