These frequencies can travel long distances by multiple reflections between the surface of the earth and its ionosphere. Used for TV, FM, and other communication purposes.
Generally travels only relatively short distances because the ionosphere is transparent to it. Present limit of radio technology for most purposes. Thermal emission of earth and planets. Solar and stellar emission. Peak of solar radiation. Visible to human eye, standard photographic film and CCD video detectors. Divided at nm by atmospheric ozone cutoff. Appreciable solar flux causes sunburn. Very strong absorption in matter, hence very difficult to observe. Electromagnetic waves with shorter wavelengths and higher frequencies include ultraviolet light, X-rays, and gamma rays.
Electromagnetic waves with longer wavelengths and lower frequencies include infrared light, microwaves, and radio and television waves. Two microwave frequencies are authorized for use in microwave ovens, and MHz.
Calculate the wavelength of each. Distances in space are often quoted in units of light years, the distance light travels in one year. How far is this in meters? The velocities of particles with thermal energy are changing almost all the time.
The particles are accelerating. Accelerating charged particles produce electromagnetic radiation. The power radiated is proportional to the square of the acceleration. Higher rates of velocity change result in higher frequency shorter wavelength radiation. The observed intensity of thermal radiation emitted by as a function of wavelength can be described by the Planck Radiation Law Physics The Planck Radiation Law gives the intensity of radiation as a function of wavelength for a fixed temperature.
The Planck law gives a continuous distribution, which peaks at some wavelength.
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