Electromagnetic Spectrum
The continuous range of electromagnetic radiation from radio waves to gamma rays, classified by frequency and wavelength.
The electromagnetic spectrum is the full range of electromagnetic radiation, ordered by frequency (and inversely by wavelength). All of it consists of oscillating electric and magnetic fields propagating at the speed of light, as described by Maxwell's equations; the different regions differ only in frequency, and therefore in energy per photon E = hf. Visible light — the tiny band human eyes detect — is just one slice of this continuum.
The spectrum is conventionally divided into bands. Radio waves (longest wavelengths, lowest frequencies) carry broadcast and communication signals. Microwaves heat food, carry satellite and radar signals, and provide the cosmic microwave background measurements of cosmology. Infrared is felt as heat, used in remote controls, thermal imaging, and spectroscopy. Visible light spans roughly 400–700 nm. Ultraviolet light ionizes atoms, causes sunburn, and drives much atmospheric chemistry. X-rays penetrate soft tissue and reveal bone structure. Gamma rays, the most energetic, come from nuclear decay and cosmic sources.
| Band | Approx. wavelength | Typical use |
|---|---|---|
| Radio | > 1 m | Broadcasting, Wi-Fi |
| Microwave | 1 mm – 1 m | Radar, satellite links |
| Infrared | 700 nm – 1 mm | Thermal imaging, remote controls |
| Visible | 400–700 nm | Human vision |
| Ultraviolet | 10–400 nm | Disinfection, sunburn |
| X-ray | 0.01–10 nm | Medical imaging |
| Gamma | < 0.01 nm | Nuclear medicine, astrophysics |
The spectrum is a single physical phenomenon, so the same laws govern all bands: the Doppler effect shifts spectral lines for astronomy, and atmospheric gases absorb and emit radiation at specific frequencies — the mechanism behind the greenhouse effect, where infrared radiation interacts with carbon dioxide and water vapor. Telescopes across the spectrum reveal different aspects of the universe, and the division into bands is practical rather than fundamental.
Tags
electromagnetic radiation light physics waves
Related articles
- Doppler Effect
- Wave–Particle Duality
- Newton's Laws of Motion
- Heisenberg Uncertainty Principle
- Maxwell's Equations
- Special Relativity
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