Unguided Transmission Media: Infrared Waves | Infrared Light

Infrared Waves/Infrared Light in Unguided Media

Key Concepts: Electromagnetic spectrum, infrared waves/light, wavelength, short wavelength radiations, long wavelength radiations, near infrared, far infrared, thermal radiation, heat waves, eavesdropping.

1. Introduction to Infrared Waves and the Electromagnetic Spectrum

• Visible light is a small portion of the electromagnetic spectrum, which ranges from 1 to 10^22 Hertz.
• The electromagnetic spectrum includes radio waves, infrared waves, visible light, ultraviolet rays, X-rays, and gamma rays.
• Infrared waves, like visible light, are a part of this spectrum.

2. Electromagnetic Spectrum and Radiation Types

• The electromagnetic spectrum encompasses all kinds of radiation, from X-rays (used in hospitals) to radio waves (used for communication).
• Radiations are broadly classified into two categories:
  • Short Wavelength Radiations: Gamma rays, X-rays, and ultraviolet rays. These have high energy and can be dangerous.
  • Long Wavelength Radiations: Radio waves, microwaves, and infrared rays. These are less harmful compared to short wavelength radiations.

3. Defining Infrared Waves/Light

• Infrared waves (or infrared light) are electromagnetic radiation with wavelengths longer than those of visible light.
• They are undetectable by the human eye.
• Most thermal radiations emitted by objects near room temperature are considered infrared waves.
• They are also referred to as heat waves, thermal waves, or electromagnetic waves due to their heat-inducing properties.
• Infrared waves are used in applications where heat production is required, such as infrared heaters and therapeutic purposes.

4. Classification of Infrared Waves

• Broad Classification:
  • Near Infrared: Used in TV remotes and photography.
  • Far Infrared: More thermal; anything generating heat (e.g., human body at 37°C) produces infrared waves.
• Detailed Classification (Five Regions):
  • Near Infrared:
    • Wavelength: 0.7 to 1.4 micrometers.
    • Applications: Fiber optics and medical field.
  • Short Wavelength Infrared:
    • Wavelength: 1.4 to 3 micrometers.
    • Applications: Telecommunication (mainly military).
  • Medium Infrared:
    • Wavelength: 3 to 8 micrometers.
    • Applications: Chemical industries and astronomical purposes.
  • Long Wavelength Infrared:
    • Wavelength: 8 to 15 micrometers.
    • Applications: Astronomical telescopes.
  • Far Infrared:
    • Wavelength: 15 to 1000 micrometers.
    • Applications: Treatment of cancers (chemotherapy).

5. Key Property: Opacity to Solid Objects

• Infrared waves do not pass through solid objects.
• This property enhances security against eavesdropping.
• Example: Standing between a TV remote and the television prevents the signal from reaching the TV.
• An infrared system in one room will not interfere with a similar system in adjacent rooms or buildings.

6. Conclusion

Infrared waves, a part of the electromagnetic spectrum, have diverse applications ranging from remote controls to cancer treatment. Their classification into near and far infrared, along with their inability to penetrate solid objects, makes them suitable for specific applications, particularly where heat generation or secure communication is required. The detailed classification based on wavelength further refines their use in various fields like medicine, telecommunications, and astronomy.