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electromagnetic spectrum

November 20, 2011

wave-like pattern – “…We may think that radio waves are completely different physical objects or events than gamma-rays. They are produced in very different ways, and we detect them in different ways. But are they really different things? The answer is ‘no’. Radio waves, visible light, X-rays, and all the other parts of the electromagnetic spectrum are fundamentally the same thing. They are all electromagnetic radiation. Electromagnetic radiation can be described in terms of a stream of photons, which are massless particles each traveling in a wave-like pattern and moving at the speed of light. Each photon contains a certain amount (or bundle) of energy, and all electromagnetic radiation consists of these photons. The only difference between the various types of electromagnetic radiation is the amount of energy found in the photons. Radio waves have photons with low energies, microwaves have a little more energy than radio waves, infrared has still more, then visible, ultraviolet, X-rays, and the most energetic of all, gamma-rays…” (Electromagnetic Spectrum)

shuttle electrons between the visible and infrared layers – “…By capturing a broader range of light waves that goes beyond traditional solar cells, the team was able to create a solar cell capable of reaching a maximum of 42% energy efficiency. “We needed a breakthrough in architecting the interface between the visible and infrared junction,” said Ted Sargent, professor of electrical and computer engineering at U of T and the leader of the research team. “[So, we] engineered a cascade – really a waterfall – of nanometres-thick materials to shuttle electrons between the visible and infrared layers.” Nanometres are a standard of measure where each unit represents one billionth of one metre. For comparison, the diameter of one strand of human hair is approximately 60,000 nanometres thick. “This advance lights up a practical path to engineering high-efficiency solar cells that make the best use of the diverse photons making up the sun’s broad palette,” said Prof. Sargent, who holds the Canada Research Chair for nanotechnology development…” (Canadian researchers shine light on the future of solar power)

distribution of electromagnetic radiation – “…TacSat-3 has far exceeded expectations in both its superior imaging performance and in its operational service life,” said Col. John Kress, Air Force Space Command, chief, Missile Warning, Missile Defense and Surveillance Operations. “The unique TacSat-3 hyperspectral imaging capability continues to provide valuable information to combatant commanders.” While ARTEMIS is focused on the visible and shortwave infrared bands, Raytheon is developing the next generation of hyperspectral systems, which will take advantage of the unique attributes of the bands of the infrared spectrum. Mid-wave IR hyperspectral sensors will be able to identify faint heat signatures from space, while long-wave IR sensors can be used to characterize effluents, such as factory plumes. “Hyperspectral sensors allow us to detect the otherwise undetectable,” said Bill Hart, vice president, Raytheon Space Systems. “Raytheon is discussing with several government customers the potential for deploying additional hyperspectral systems, either as a single, multiband system or a constellation of disaggregated capabilities.” Raytheon Company, with 2010 sales of $25 billion, is a technology and innovation leader specializing in defense, homeland security and other government markets throughout the world. With a history of innovation spanning 89 years, Raytheon provides state-of-the-art electronics, mission systems integration and other capabilities in the areas of sensing; effects; and command, control, communications and intelligence systems, as well as a broad range of mission support services. With headquarters in Waltham, Mass., Raytheon employs 72,000 people worldwide…” (Raytheon’s First-of-Its-Kind Space-Based Hyperspectral Sensor Marks Second Year on Orbit)

fertilizer to spray – “…RapidEye is based in Germany but they have a view of the entire world thanks to their fleet of five satellites. Using spectral analysis, they can tell any farmer, anywhere in the world how to best manage their land without ever leaving the office. Each individual satellites focuses on a specific band of the electromagnetic spectrum; by compiling this data, RapidEye can determine the fertility of any plot of land in the world (so long as there aren’t any clouds). They then relay this information to their clients who range from cotton farmers in North Carolina to wheat producers in Kazakhstan. Using the images provided to them, farmers can then determine exactly what fertilizer to spray, where to spray it, and how much to use…” (Why Satellites are the New God for Farmers)

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The “electromagnetic spectrum” of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object. The electromagnetic spectrum extends from low frequencies used for modern radio to gamma radiation at the short-wavelength end, covering wavelengths from thousands of kilometers down to a fraction of the size of an atom. The long wavelength limit is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length, although in principle the spectrum is infinite and continuous (Wikepedia).


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