Прочитайте текст и выполните задания. A mechanical wave 1. A mechanical wave is a wave that propagat...: ответ на тест 1088080 - Английский язык

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A mechanical wave
1. A mechanical wave is a wave that propagates as an oscillation of matter, and therefore transfers energy through a medium. While waves can move over long distances, the movement of the medium of transmission – the material – is limited. Therefore, oscillating material does not move far from its initial equilibrium position. Mechanical waves transport energy only. This energy propagates in the same direction as the wave. Any kind of wave (mechanical or electromagnetic) has a certain energy. No material is transported as a result of mechanical waves. Mechanical wave can be produced only in media which possess elasticity and inertia.
2. A mechanical wave requires an initial energy input. Once this initial energy is added, the wave travels through the medium until all its energy is transferred. In contrast, electromagnetic waves require no medium, but can still travel through one.
3. One important property of mechanical waves is that their amplitudes possess an unusual form, displacement divided by reduced wavelength. When this gets comparable to unity, significant nonlinear effects such as harmonic generation may occur, and, if large enough, may result in chaotic effects. For example, waves on the surface of a body of water break when this dimensionless amplitude exceeds 1, resulting in a foam on the surface and turbulent mixing. Some of the most common examples of mechanical waves can be water waves, sound waves etc.
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A mechanical wave
1. A mechanical wave is a wave that propagates as an oscillation of matter, and therefore transfers energy through a medium. While waves can move over long distances, the movement of the medium of transmission – the material – is limited. Therefore, oscillating material does not move far from its initial equilibrium position. Mechanical waves transport energy only. This energy propagates in the same direction as the wave. Any kind of wave (mechanical or electromagnetic) has a certain energy. No material is transported as a result of mechanical waves. Mechanical wave can be produced only in media which possess elasticity and inertia.
2. A mechanical wave requires an initial energy input. Once this initial energy is added, the wave travels through the medium until all its energy is transferred. In contrast, electromagnetic waves require no medium, but can still travel through one.
3. One important property of mechanical waves is that their amplitudes possess an unusual form, displacement divided by reduced wavelength. When this gets comparable to unity, significant nonlinear effects such as harmonic generation may occur, and, if large enough, may result in chaotic effects. For example, waves on the surface of a body of water break when this dimensionless amplitude exceeds 1, resulting in a foam on the surface and turbulent mixing. Some of the most common examples of mechanical waves can be water waves, sound waves etc.
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What differentiates mechanical waves from electromagnetic ones?

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The European Organization for Nuclear Research
1. The European Organization for Nuclear Research, known as CERN (in French Conseil Européen pour la Recherche Nucléaire (European Council for Nuclear Research) is an international organization whose purpose is to operate the world’s largest particle physics laboratory. Established in 1954, the organization is based in the northwest suburbs of Geneva on the Franco-Swiss border. CERN has 20 European member states. It employs 2,400 full-time employees, 1,500 part-time employees, and hosts some 10,000 visiting scientists and engineers, representing 608 universities and research facilities and 113 nationalities.
2. Although after the laboratory’s establishment, its work went beyond the study of the atomic nucleus into higher-energy physics, its original aims have remained the same. These are to sponsor and help organize research projects that will lead to a better understanding of the universe, to push to the limit advances in different technologies, to educate the scientists of the future and to encourage international cooperation through science.
3. The main scientific instruments at CERN are particle accelerators and particle detectors. Scientists use accelerators to send beams of particles towards each other at very high energy. They then cause the particles to collide with each other or with stationary targets and observe and record the results with the detectors. CERN is famously home to the Large Hadron Collider (LHC), which, with a circumference of 27 km, is the largest and most powerful particle accelerator in the world.
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Ancient Martian Conditions Could Have Supported Life
1. The American space agency recently reported that the planet Mars once could have supported micro-organisms, extremely small life forms. The announcement came after the agency’s Curiosity rover examined a rock on Mars. It was the first sample of rock powder ever collected and tested on the red planet. Curiosity used a drill on its two-meter long robotic arms to cut into the rock and collect about ten grams of powder. Space agency officials called the drilling, the biggest success for the Curiosity team since the rover landed on Mars in August, 2012.
2. After the drilling was done and the powder collected, the small laboratory on Curiosity began a series of tests. American scientists said the test results led them to believe there was once life on Mars. The rock sample came from an area on Mars called Yellowknife Bay. The area had some of the chemicals required to support life as we know it. They include oxygen, hydrogen, nitrogen and carbon. Scientists believe Mars was once a warmer, wetter environment before turning into a freezing dry desert. Researchers say the Martian bedrock showed evidence of many periods of wet conditions. And they say there are clay minerals in the rock sample. These minerals are evidence of water.
3. The project is expected to last two years and cost $2.5 billion. Curiosity is not designed to look for microbes that may be alive on Mars today or inspect remains of life forms that no longer exist. Curiosity is the first Mars rover, but not the only one. The American space agency says it plans to send another rover, called Opportunity, to the red planet in 2020. Opportunity would be part of NASA’s plan to explore the Martian surface and atmosphere. The agency hopes to send humans to Mars in about 20 years.
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The History of the Laser
1. Laser is short for Light Amplification by Stimulated Emission of Radiation. The idea behind lasers is complex. Theodore Maiman succeeded in building the first working laser in 1960. He worked at Hughes Research Laboratories in Malibu, California. Before the laser, scientists developed a similar device: a maser which stands for Microwave Amplification by Stimulated Emission of Radiation. A maser is basically a microwave version of the laser. Microwaves are a form of electromagnetic radiation similar to, but shorter than, radio waves. The best-known use of masers is in highly accurate clocks.
2. In the 1950s, researchers in the United States and Russia independently developed the technology that made both masers and lasers possible. Charles Townes was a professor at the Massachusetts Institute of Technology in Cambridge, Massachusetts. He and his students developed the first maser. Russians Nicolay Basov and Aleksander Prokhorov did their research in Moscow. Their work led to technology important to lasers and masers. The three men received the Nobel Prize in Physics in 1964.
3. The physics of the laser may be complex. Still, it is just a story of how electrons interact with light. When a light particle, or photon, hits an electron, the electron jumps to a higher energy state. If another photon strikes one of these high-energy electrons, the electron releases two photons that travel together at the same wavelength. When this process is repeated enough, lots of organized, or coherent, photons are produced.
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Containing the Sun – the challenges facing ITER
1. Pierre-Gilles de Gennes, winner of the Nobel Prize for Physics, famously declared: «We say that we will put the sun into a box. The idea is pretty. The problem is, we don’t know how to make the box». He was talking about nuclear fusion reactors, and the «box» is the casing of the reactor. But what should the box be made of? This is the problem that materials scientists around the world are working on in preparation for the construction of ITER (International Thermonuclear Experimental Reactor).
2. ITER will be the next stage of research into nuclear fusion, and aims to pave the way for commercial fusion reactors by developing the necessary technologies and processes. The reactor will reproduce the nuclear reactions that occur in the sun using super-heated gas, or plasma, in a tokamak. The tokamak generates an intense doughnut-shaped magnetic field which confines the plasma and allows fusion to take place.
3. The ITER fusion reactor itself has been designed to produce 500 megawatts of output power for 50 megawatts of input power, or ten times the amount of energy put in. The machine is expected to demonstrate the principle of producing more energy from the fusion process than is used to initiate it, something that has not yet been achieved with previous fusion reactors.
4. ITER is currently building the world’s largest experimental tokamak nuclear fusion reactor at the Cadarache facility in the south of France. The project is funded and run by seven member entities – the European Union (EU), India, Japan, China, Russia, South Korea and the United States. Construction of the facility began in 2007, and the first plasma is expected to be produced in 2020.
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