Electromagnetic radiation

• Radiation consisting of excited photons in varying frequencies
• Certain categories overlap; boundary between types not strict, and categories are as much from radiative source as from energy level
• From least to most generally energetic:
  • Non-ionizing
    • Radio
      • Often used for STL communications
      • Ranges <1.24 µeV
    • Microwave
      • Ranges from 1.24 µeV–1.24 meV
    • Infrared
      • Ranges from 1.24 meV-1.7 eV
    • Visible light
      • Ranges from 1.7-3.1 eV
  • Ionizing
    • Ultraviolet
      • Ranges from 3.1-120 eV
    • X-ray
      • Divided into soft X-rays (~100 eV-10 keV) and hard X-rays (10+ keV)
      • Usually no more energetic than ~120 keV, but can be produced with energies upwards of 1 MeV; such are known as high-energy x-rays, or HEX-rays
      • HEX-rays distinguished from low-energy gamma radiation by source: charged particles colliding with matter
    • Gamma
      • Generally 125+ keV, but some nuclear decay detected as low as 0.08 keV
      • Low-energy gamma radiation distinguished from HEX-rays by source: produced by the nucleus of an atom, often through radioactive decay
• General properties