The ancient Greeks recognized that light traveled in straight lines and studied some of its properties, including reflection and refraction. Humans have always been aware of visible light and radiant heat but for most of history it was not known that these phenomena were connected or were representatives of a more extensive principle. See also: History of electromagnetism, History of radio, History of electrical engineering, and History of optics Spectroscopy is used to study the interactions of electromagnetic waves with matter. Throughout most of the electromagnetic spectrum, spectroscopy can be used to separate waves of different frequencies, producing a spectrum of the constituent frequencies. Radiation of visible light and longer wavelengths are classified as nonionizing radiation because they have insufficient energy to cause these effects. Extreme ultraviolet, soft X-rays, hard X-rays and gamma rays are classified as ionizing radiation because their photons have enough energy to ionize atoms, causing chemical reactions. There is no known limit for long and short wavelengths. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names beginning at the low-frequency (long-wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 10 25 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. National Aeronautics and Space Administration.Entire range of frequencies of electromagnetic radiation Class "Introduction to the Electromagnetic Spectrum" NASA Science. Retrieved, from NASA Science website: MLA Introduction to the Electromagnetic Spectrum. National Aeronautics and Space Administration, Science Mission Directorate. Top of Page | Next: Anatomy of an Electromagnetic Wave ![]() Instruments have to be positioned above Earth's energy-absorbing atmosphere to "see" higher energy and even some lower energy light sources such as quasars. While our atmosphere is essential to protecting life on Earth and keeping the planet habitable, it is not very helpful when it comes to studying sources of high-energy radiation in space. These regions of the spectrum with wavelengths that can pass through the atmosphere are referred to as "atmospheric windows." Some microwaves can even pass through clouds, which make them the best wavelength for transmitting satellite communication signals. Some radiation, such as visible light, largely passes (is transmitted) through the atmosphere. Seeing Beyond our Atmosphere - NASAspacecraft, such as RHESSI, provide scientistswith a unique vantage point, helping them"see" at higher-energy wavelengths that areblocked by the Earth's protective atmosphere.Įlectromagnetic radiation is reflected or absorbed mainly by several gases in the Earth's atmosphere, among the most important being water vapor, carbon dioxide, and ozone.
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