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Radio waves, at the low-frequency end of the spectrum, have the lowest photon energy and the longest wavelengths—thousands of kilometers, or more. They can be emitted and received by antennas , and pass through the atmosphere, foliage, and most building materials.
Radio waves were first predicted by the theory of electromagnetism that was proposed in 1867 by Scottish mathematical physicist James Clerk Maxwell. [5] His mathematical theory, now called Maxwell's equations, predicted that a coupled electric and magnetic field could travel through space as an "electromagnetic wave".
Radio waves are defined by the ITU as: "electromagnetic waves of frequencies arbitrarily lower than 3000 GHz, propagated in space without artificial guide". [5] At the high frequency end the radio spectrum is bounded by the infrared band. The boundary between radio waves and infrared waves is defined at different frequencies in different ...
In order of increasing frequency and decreasing wavelength, the electromagnetic spectrum includes: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. [ 3 ] [ 4 ] Electromagnetic waves are emitted by electrically charged particles undergoing acceleration , [ 5 ] [ 6 ] and these waves can subsequently interact ...
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]
Medical applications of radio frequency (RF) energy, in the form of electromagnetic waves (radio waves) or electrical currents, have existed for over 125 years, [9] and now include diathermy, hyperthermy treatment of cancer, electrosurgery scalpels used to cut and cauterize in operations, and radiofrequency ablation. [10]
Sound waves created by a supermassive black hole in the Perseus cluster [1] 10 −14: 10 fHz ~31.71 fHz: Once every one million years 10 −12: 1 picohertz (pHz) 1.23 pHz Precession of the Earth's axis (about every 25,700 years) 10 −11: 10 pHz ~31.71 pHz: Once per millennium 10 −10: 100 pHz ~317.1 pHz: Once per century 10 −9: 1 nanohertz ...
[1] [2] It is in the microwave part of the radio spectrum, between the super high frequency band and the terahertz band. Radio waves in this band have wavelengths from ten to one millimeter, so it is also called the millimeter band and radiation in this band is called millimeter waves, sometimes abbreviated MMW or mmWave. [3]