EMspekteret

EMspekteret, or the electromagnetic spectrum, refers to the range of all electromagnetic radiation, arranged by wavelength or frequency. In a vacuum, electromagnetic waves propagate at the speed of light, about 299,792 kilometers per second. The spectrum spans from radio waves with the longest wavelengths through microwaves, infrared, visible light, ultraviolet, X-rays, to gamma rays with the shortest wavelengths. A commonly used subdivision includes radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma-ray bands; the terahertz region lies between microwaves and infrared.

Key relationships: wavelength λ and frequency f are linked by c = λ f; photon energy E = h f = hc/λ. Longer wavelengths carry lower energy per photon; shorter wavelengths higher energy.

Interactions with matter and detection differ across the spectrum. Radio waves are detected with antennas; infrared with bolometers and photodiodes; visible with cameras and photodetectors; ultraviolet to gamma require specialized detectors such as photomultiplier tubes, scintillators, CCDs, and space-based instrumentation due to atmospheric absorption.

Significance and applications: The spectrum underpins communications (radio, TV, mobile), remote sensing, spectroscopy, astronomy, and medical imaging (X-ray). The atmosphere is transparent to certain bands but absorbs others, notably much of the ultraviolet and X-ray regions, shaping observational astronomy and aviation safety.

Safety: Ionizing radiation in the high-energy end (UV above, X-rays, gamma) can damage living tissue; appropriate shielding and exposure limits are used.