1.2: Electromagnetic Spectrum
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- Jul 7, 2024
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Electromagnetic fields exist at frequencies from DC (0 Hz) to at least 1020 Hz – that’s at least 20 orders of magnitude! At DC, electromagnetics consists of two distinct disciplines: electrostatics, concerned with electric fields; and magnetostatics, concerned with magnetic fields. At higher frequencies, electric and magnetic fields interact to form propagating waves. Waves having frequencies within certain ranges are given names based on how they manifest as physical phenomena. These names are (in order of increasing frequency): radio, infrared (IR), optical (also known as “light”), ultraviolet (UV), X-rays, and gamma rays (γ-rays). See Table
Definition: Electromagnetic Spectrum
The term electromagnetic spectrum refers to the various forms of electromagnetic phenomena that exist over the continuum of frequencies
The speed (properly known as “phase velocity”) at which electromagnetic fields propagate in free space is given the symbol
Table
Regime | Frequency Range | Wavelength Range |
---|---|---|
< 0.01 nm | ||
X-Ray | 10–0.01 nm | |
Ultraviolet (UV) | 120–10 nm | |
Optical | 700–120 nm | |
Infrared (IR) | 1 mm – 700 nm | |
Radio | 100 km – 1 mm |
The radio portion of the electromagnetic spectrum alone spans 12 orders of magnitude in frequency (and wavelength), and so, not surprisingly, exhibits a broad range of phenomena. This is shown in Figure

Band | Frequencies | Wavelengths | Typical Applications |
---|---|---|---|
EHF | 30-300 GHz | 10–1 mm | 60 GHz WLAN, Point-to-point data links |
SHF | 3–30 GHz | 10–1 cm | Terrestrial & Satellite data links, Radar |
UHF | 300–3000 MHz | 1–0.1 m | TV broadcasting, Cellular, WLAN |
VHF | 30–300 MHz | 10–1 m | FM & TV broadcasting, LMR |
HF | 3–30 MHz | 100–10 m | Global terrestrial comm., CB Radio |
MF | 300–3000 kHz | 1000–100 m | AM broadcasting |
LF | 30–300 kHz | 10–1 km | Navigation, RFID |
VLF | 3–30 kHz | 100–10 km | Navigation |
Band | Frequencies | Wavelengths |
---|---|---|
Violet | 668–789 THz | 450–380 nm |
Blue | 606–668 THz | 495–450 nm |
Green | 526–606 THz | 570–495 nm |
Yellow | 508–526 THz | 590–570 nm |
Orange | 484–508 THz | 620–590 nm |
Red | 400–484 THz | 750–620 nm |