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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]
Thus, higher frequency photons have more energy. For example, a 10 20 Hz gamma ray photon has 10 19 times the energy of a 10 1 Hz extremely low frequency radio wave photon. The effects of EMR upon chemical compounds and biological organisms depend both upon the radiation's power and its frequency.
The oscillating electrons in the antenna generate oscillating electric and magnetic fields that radiate away from the antenna as radio waves. In reception of radio waves, the oscillating electric and magnetic fields of a radio wave couple to the electrons in an antenna, pushing them back and forth, creating oscillating currents which are ...
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 ...
The duty cycle for a pulsed radio frequency is the percent time the RF packet is on, 4.2% for this example ([0.042 ms × 1000 pulses divided by 1000 ms/s] × 100). The pulse packet form can be a square, triangle, sawtooth or sine wave. [1] In several applications of pulse radio frequency, such as radar, [2] times between pulses can be modulated.
Artificially generated radio waves are used for fixed and mobile radio communication, broadcasting, radar and other navigation systems, satellite communication, computer networks and innumerable other applications. In addition, almost any wire carrying alternating current will radiate some of the energy away as radio waves; these are mostly ...
For example, see computation of radio wave attenuation in the atmosphere used in satellite link design. In meteorology and climatology , global and local temperatures depend in part on the absorption of radiation by atmospheric gases (such as in the greenhouse effect ) and land and ocean surfaces (see albedo ).