It's OK to Ask 'Em to Work: and Other Essential Maxims for Smart Managers

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Herschel Discovers Infrared Light". Cool Cosmos Classroom activities. Archived from the original on 2012-02-25 . Retrieved 4 March 2013. He directed sunlight through a glass prism to create a spectrum […] and then measured the temperature of each colour. […] He found that the temperatures of the colours increased from the violet to the red part of the spectrum. […] Herschel decided to measure the temperature just beyond the red of the spectrum in a region where no sunlight was visible. To his surprise, he found that this region had the highest temperature of all. The distinction between X-rays and gamma rays is partly based on sources: the photons generated from nuclear decay or other nuclear and subnuclear/particle process are always termed gamma rays, whereas X-rays are generated by electronic transitions involving highly energetic inner atomic electrons. [7] [8] [9] In general, nuclear transitions are much more energetic than electronic transitions, so gamma rays are more energetic than X-rays, but exceptions exist. By analogy to electronic transitions, muonic atom transitions are also said to produce X-rays, even though their energy may exceed 6 megaelectronvolts (0.96pJ), [10] whereas there are many (77 known to be less than 10keV (1.6fJ)) low-energy nuclear transitions ( e.g., the 7.6eV (1.22aJ) nuclear transition of thorium-229m), and, despite being one million-fold less energetic than some muonic X-rays, the emitted photons are still called gamma rays due to their nuclear origin. [11]

Terahertz radiation or sub-millimeter radiation is a region of the spectrum from about 100GHz to 30 terahertz (THz) between microwaves and far infrared which can be regarded as belonging to either band. Until recently, the range was rarely studied and few sources existed for microwave energy in the so-called terahertz gap, but applications such as imaging and communications are now appearing. Scientists are also looking to apply terahertz technology in the armed forces, where high-frequency waves might be directed at enemy troops to incapacitate their electronic equipment. [15] Terahertz radiation is strongly absorbed by atmospheric gases, making this frequency range useless for long-distance communication. It’s challenging to avoid flying altogether, but some companies suggest low-carbon options where possible. In 1800, William Herschel discovered infrared radiation. [2] He was studying the temperature of different colours by moving a thermometer through light split by a prism. He noticed that the highest temperature was beyond red. He theorized that this temperature change was due to "calorific rays", a type of light ray that could not be seen. The next year, Johann Ritter, working at the other end of the spectrum, noticed what he called "chemical rays" (invisible light rays that induced certain chemical reactions). These behaved similarly to visible violet light rays, but were beyond them in the spectrum. [3] They were later renamed ultraviolet radiation. L'Annunziata, Michael; Baradei, Mohammad (2003). Handbook of Radioactivity Analysis. Academic Press. p.58. ISBN 978-0-12-436603-9.

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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. There is no known limit for long and short wavelengths. 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. Radiation of visible light and longer wavelengths are classified as nonionizing radiation because they have insufficient energy to cause these effects. For instance, Exodus offers train travel alternatives on many of its European trips. It estimates that taking the train from London to Naples (one way) produces only 10.2kg of CO2 compared with 254kg if you take a flight in economy from London to Naples. On top of this, it has bumped up its selection of UK tours to offer more sustainable choices closer to home. See also: History of electromagnetic theory, History of radio, History of electrical engineering, and History of optics Collective oscillation of charge carriers in bulk material ( plasma oscillation). An example would be the oscillatory travels of the electrons in an antenna.

Next in frequency comes ultraviolet (UV). The wavelength of UV rays is shorter than the violet end of the visible spectrum but longer than the X-ray. Chris seems nice but honestly, he’s like a man-child with those Kinder eggs! What’s all that about? I feel so sorry for him when he’s trying to sleep and Em just keeps chatting, vlogging and shoving the camera right in his face, ugh!!Maxwell's predicted waves included waves at very low frequencies compared to infrared, which in theory might be created by oscillating charges in an ordinary electrical circuit of a certain type. Attempting to prove Maxwell's equations and detect such low frequency electromagnetic radiation, in 1886, the physicist Heinrich Hertz built an apparatus to generate and detect what are now called radio waves. Hertz found the waves and was able to infer (by measuring their wavelength and multiplying it by their frequency) that they traveled at the speed of light. Hertz also demonstrated that the new radiation could be both reflected and refracted by various dielectric media, in the same manner as light. For example, Hertz was able to focus the waves using a lens made of tree resin. In a later experiment, Hertz similarly produced and measured the properties of microwaves. These new types of waves paved the way for inventions such as the wireless telegraph and the radio. f = c λ , or f = E h , or E = h c λ , {\displaystyle f={\frac {c}{\lambda }},\quad {\text{or}}\quad f={\frac {E}{h}},\quad {\text{or}}\quad E={\frac {hc}{\lambda }},} UV is the longest wavelength radiation whose photons are energetic enough to ionize atoms, separating electrons from them, and thus causing chemical reactions. Short wavelength UV and the shorter wavelength radiation above it (X-rays and gamma rays) are called ionizing radiation, and exposure to them can damage living tissue, making them a health hazard. UV can also cause many substances to glow with visible light; this is called fluorescence. At most wavelengths, however, the information carried by electromagnetic radiation is not directly detected by human senses. Natural sources produce EM radiation across the spectrum, and technology can also manipulate a broad range of wavelengths. Optical fiber transmits light that, although not necessarily in the visible part of the spectrum (it is usually infrared), can carry information. The modulation is similar to that used with radio waves. Microwaves are radio waves of short wavelength, from about 10 centimeters to one millimeter, in the SHF and EHF frequency bands. Microwave energy is produced with klystron and magnetron tubes, and with solid state devices such as Gunn and IMPATT diodes. Although they are emitted and absorbed by short antennas, they are also absorbed by polar molecules, coupling to vibrational and rotational modes, resulting in bulk heating. Unlike higher frequency waves such as infrared and visible light which are absorbed mainly at surfaces, microwaves can penetrate into materials and deposit their energy below the surface. This effect is used to heat food in microwave ovens, and for industrial heating and medical diathermy. Microwaves are the main wavelengths used in radar, and are used for satellite communication, and wireless networking technologies such as Wi-Fi. The copper cables ( transmission lines) which are used to carry lower-frequency radio waves to antennas have excessive power losses at microwave frequencies, and metal pipes called waveguides are used to carry them. Although at the low end of the band the atmosphere is mainly transparent, at the upper end of the band absorption of microwaves by atmospheric gases limits practical propagation distances to a few kilometers.

Generally, electromagnetic radiation is classified by wavelength into radio wave, microwave, infrared, visible light, ultraviolet, X-rays and gamma rays. The behavior of EM radiation depends on its wavelength. When EM radiation interacts with single atoms and molecules, its behavior also depends on the amount of energy per quantum (photon) it carries. Main article: Microwaves Plot of Earth's atmospheric opacity to various wavelengths of electromagnetic radiation. This is the surface-to-space opacity, the atmosphere is transparent to longwave radio transmissions within the troposphere but opaque to space due to the ionosphere. Plot of atmospheric opacity for terrestrial to terrestrial transmission showing the molecules responsible for some of the resonances Davidson, Michael W. "Johann Wilhelm Ritter (1776–1810)". The Florida State University . Retrieved 5 March 2013. Ritter […] hypothesized that there must also be invisible radiation beyond the violet end of the spectrum and commenced experiments to confirm his speculation. He began working with silver chloride, a substance decomposed by light, measuring the speed at which different colours of light broke it down. […] Ritter […] demonstrated that the fastest rate of decomposition occurred with radiation that could not be seen, but that existed in a region beyond the violet. Ritter initially referred to the new type of radiation as chemical rays, but the title of ultraviolet radiation eventually became the preferred term. Electromagnetic radiation with a wavelength between 380 nm and 760nm (400–790 terahertz) is detected by the human eye and perceived as visible light. Other wavelengths, especially near infrared (longer than 760nm) and ultraviolet (shorter than 380nm) are also sometimes referred to as light, especially when the visibility to humans is not relevant. White light is a combination of lights of different wavelengths in the visible spectrum. Passing white light through a prism splits it up into the several colours of light observed in the visible spectrum between 400nm and 780nm.Molecular electron excitation (including pigment molecules found in the human retina), plasma oscillations (in metals only)