Overview
This lecture covers the practical applications and characteristics of various regions of the electromagnetic spectrum, including radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays.
Electromagnetic Radiation Overview
- Radiation is energy transmitted as waves or particles through space or matter.
- Non-ionizing radiation includes visible light and radio waves; ionizing radiation includes some UV, x-rays, and gamma rays.
Radio Waves and Applications
- Radio waves have the longest wavelengths and are used for wireless communications (radio, TV).
- Radio waves are produced by vibrating electrons in antennas.
- AM (amplitude modulation) and FM (frequency modulation) are two broadcast methods; AM changes amplitude, FM changes frequency.
- Radio waves are allocated into frequency bands for different services.
- AM radio operates around 1 million hertz; FM radio around 100 million hertz.
- The ionosphere and satellites are used to reflect and relay radio waves globally.
Microwaves and Their Uses
- Microwaves penetrate the atmosphere for satellite communications.
- Used in satellite and cable TV, radar, and cellular phones.
- Radar uses microwaves to detect and locate objects using reflection.
- Microwave ovens heat food by agitating water molecules.
Infrared Radiation
- Infrared waves range from millimeters to microscopic lengths and are associated with heat.
- Longer wavelengths produce heat; shorter wavelengths are used in remote controls and imaging.
- Applications include remote controls, night vision, infrared cameras, and medical imaging.
Visible Light
- Visible spectrum ranges from 4 × 10⁻⁷ to 7 × 10⁻⁷ meters in wavelength.
- Essential for photosynthesis and is used in artificial lighting and optical fibers.
- Produced by incandescent, fluorescent, and neon lights.
Ultraviolet Radiation
- UV lies just beyond visible light, with shorter wavelengths and higher energy.
- The sun is the primary source; artificial sources include UV lamps.
- UV is used for sterilizing water, verifying banknotes, and aiding vitamin D production.
X-Rays
- X-rays have shorter wavelengths and more energy than UV rays.
- Used in medical diagnostics (bone scans) and industry (inspecting welded joints).
Gamma Rays
- Gamma rays have the shortest wavelengths and highest frequencies.
- Emitted by energetic cosmic and terrestrial sources; highly penetrating and destructive.
- Used in cancer treatment (radiotherapy) and sterilization.
Key Terms & Definitions
- Radiation — Transmission of energy as waves or particles.
- Non-ionizing radiation — Radiation not energetic enough to ionize atoms.
- Ionizing radiation — Radiation that can remove electrons from atoms, forming ions.
- AM (Amplitude Modulation) — Modulation method changing wave amplitude.
- FM (Frequency Modulation) — Modulation method changing wave frequency.
- Ionosphere — Atmospheric layer of ionized gases that reflects radio waves.
- Radar — System using microwaves to detect object location and distance.
- Photosynthesis — Process by which plants convert light energy to chemical energy.
Action Items / Next Steps
- Review the summary table of electromagnetic wave applications.
- Prepare for the next lesson on the effects of electromagnetic radiation on living things and the environment.