Practical Applications of Electromagnetic Waves

Introduction

• Radiation: Transmission of energy in the form of waves or particles.
  • Non-ionizing radiation: Visible light, ultraviolet light (partially ionizing), TV and radio signals.
  • Ionizing radiation: X-rays, radiation from nuclear medicine.

Radio Waves

• Enabled wireless communication over long distances.
• Production: Created by vibrating electrons in an antenna.
• Uses:
  • AM (Amplitude Modulation): Changes amplitude to match audio frequency, used for long-distance broadcasting.
  • FM (Frequency Modulation): Changes frequency to match signal, provides higher quality broadcasting.
• Transmission and Reception:
  • Received by antennas and converted back to sound/pictures.
  • Divided into wave bands for specific services by law.
• Frequency:
  • AM:
    • Example: 630 AM = 630,000 Hz.
  • FM:
    • Example: 101.1 FM = 101,100,000 Hz.
• Ionosphere: Reflects high-frequency radio waves for global communication.

Microwaves

• Penetrate Earth's atmosphere, used in satellite communications.
• Transmission:
  • Signals from antennas to satellites, retransmitted globally.
  • Used for telephone services, TV broadcasting, scientific research, and weather forecasts.
• Radar:
  • System with antenna, transmitter, and receiver.
  • Sends microwaves to detect object distance and direction.
• Cable TV:
  • Uses microwaves for news transmission.
  • Broadcasted live globally.
• Cell Phones:
  • Use networks of cells with towers for mobile communication.
• Microwave Ovens:
  • Heat food by agitating water molecules internally.

Infrared Waves

• Lie in the lower middle frequency range.
• Longer wavelengths produce heat (e.g., fire, sun), shorter for remote controls.
• Applications:
  • Infrared Photography: Details of Earth's vegetation.
  • Medical Diagnosis: Infrared scanners show body temperature variations.
  • Remote Controls: Emit infrared signals.
  • Night Vision Goggles: Allow vision in dark.

Visible Light

• Essential for photosynthesis.
• Produced by luminous objects through incandescent, fluorescent, and neon lights.
• Applications:
  • Incandescent Light: From heated tungsten filament.
  • Fluorescent Light: Cooler, less energy, uses gas molecules.
  • Neon Light: Produced by electrons in gases, common in signage.

Ultraviolet Radiation

• Shorter wavelengths, higher energy than visible light.
• Main source: Sun.
• Applications:
  • Banks: UV lamps check signatures on passbooks.
  • Sterilization: Water fountains.
  • Laundry Detergents: Fluorescent chemicals glow in sunlight.

X-rays

• Shorter wavelengths, higher energy.
• Produced by fast-moving electrons.
• Uses:
  • Medical: Diagnose bone fractures, tumors.
  • Industrial: Inspect welded joints.

Gamma Rays

• Shortest wavelength, highest frequency.
• Sources: Cosmic events, nuclear reactions.
• Applications:
  • Medicine: Cancer treatment (radiotherapy).
  • Sterilization: Water purification.

Summary Table

• Radio Waves: Radio, TV communication.
• Microwaves: Satellite and terrestrial communication, radar, ovens.
• Infrared Rays: Remote controls, medical imaging, night vision goggles.
• Visible Light: Photosynthesis, artificial lighting, medical uses.
• Ultraviolet Rays: Sterilization, banknote authentication.
• X-rays: Medical and industrial applications.
• Gamma Rays: Medical and industrial applications.

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• Next Topic: Effects of electromagnetic radiation on living things and the environment.