Wavebands

Wavebands are portions of the electromagnetic spectrum grouped by wavelength. The term is conventional and practical, with boundaries that vary by discipline. The major divisions—radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma—are widely used in science and engineering to describe how electromagnetic radiation is produced, detected, and used.

Radio waves have wavelengths longer than about 1 millimeter and include the bands used for broadcasting and long-distance communication as well as radar. Microwaves span roughly from 1 millimeter to 30 centimeters and are central to radar, wireless links, and many industrial processes. Infrared radiation covers about 0.7 micrometers to 1 millimeter, and is grouped into near, mid, and far infrared; it is important for thermal imaging and spectroscopy. Visible light ranges from about 380 to 750 nanometers and is the spectrum perceptible to the eye. Ultraviolet, from roughly 10 to 400 nanometers, is associated with fluorescence, sterilization, and high-energy interactions. X-rays span about 0.01 to 10 nanometers and are used in medical imaging and materials analysis. Gamma rays are shorter than about 0.01 nanometers, produced by radioactive decay and high-energy processes, with applications in medicine and astrophysics.

Atmospheric transparency varies by band: long-wavelength radio and some infrared windows pass through with less attenuation, while ultraviolet, X-ray, and gamma radiation are largely blocked by air. Observations and applications therefore rely on ground-based instruments for some bands and space- or high-altitude platforms for others. Instrumentation across wavebands includes antennas and receivers, infrared cameras, optical telescopes, ultraviolet sensors, X-ray detectors, and gamma-ray spectrometers.