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Photoelectric effect The photoelectric effect is the emeyission of electrons or other free carriers when light shines on a material. Electrons emitted in this manner can be called photo electrons. This phenomenon is commonly studied in electronic physics, as well as in fields of chemistry, such as quantum chemistry or electrochemistry. According to classical electromagnetic theory, this effect can be attributed to the transfer of energy from the light to an electron. From this perspective, an alteration in the intensity of light would induce changes in the kinetic energy of the electrons emitted from the metal. Furthermore, according to this theory, a sufficiently dim light would be expected to show a time lag between the initial shining of its light and the subsequent emission of an electron. However, the experimental results did not correlate with either of the two predictions made by classical theory. Instead, electrons are dislodged only by the impingement of photons when tho...

Thermodynamics Annotated color version of the original 1824 Carnot heat engine showing the hot body (boiler), working body (system, steam), and cold body (water), the letters labeled according to the stopping points in Carnot cycle. Thermodynamics is a branch of physics concerned with heat and temperature and their relation to energy and work. The behavior of these quantities is governed by the four laws of thermodynamics, irrespective of the composition or specific properties of the material or system in question. The laws of thermodynamics are explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, chemical engineering and mechanical engineering. Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines, particularly through the work of French physicist Nicolas Léonard Sadi Carnot (1824) who believed that e...

Comparison to Copernicus Edit Kepler's laws improve the model of Copernicus. If the eccentricities of the planetary orbits are taken as zero, then Kepler basically agrees with Copernicus: The planetary orbit is a circle The Sun is at the center of the orbit The speed of the planet in the orbit is constant The eccentricities of the orbits of those planets known to Copernicus and Kepler are small, so the foregoing rules give good approximations of planetary motion; but Kepler's laws fit the observations better than Copernicus'. Kepler's corrections are not at all obvious: The planetary orbit is not a circle, but an ellipse. The Sun is not at the center but at a focal point of the elliptical orbit. Neither the linear speed nor the angular speed of the planet in the orbit is constant, but the area speed is constant. The eccentricity of the orbit of the Earth makes the time from the March equinox to the September equinox, around 186 days, unequal to the time ...

Radar For other uses, see Radar (disambiguation). Long-range radar antenna, used to track space objects and ballistic missiles. Radar of the type used for detection of aircraft. It rotates steadily, sweeping the airspace with a narrow beam. Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the object(s). Radio waves (pulsed or continuous) from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed. Radar was developed secretly for military use by several nati...

Communication Communication (from Latin commūnicāre, meaning "to share"[1]) is the act of conveying intended meanings from one entity or group to another through the use of mutually understood signs and semiotic rules. The main steps inherent to all communication are: [2] The formation of communicative motivation or reason. Message composition (further internal or technical elaboration on what exactly to express). Message encoding (for example, into digital data, written text, speech, pictures, gestures and so on). Transmission of the encoded message as a sequence of signals using a specific channel or medium. Noise sources such as natural forces and in some cases human activity (both intentional and accidental) begin influencing the quality of signals propagating from the sender to one or more receivers. Reception of signals and reassembling of the encoded message from a sequence of received signals. Decoding of the reassembled encoded message. Interpretation an...

Pendulum For other uses, see Pendulum (disambiguation). "Simple gravity pendulum" model assumes no friction or air resistance. A pendulum is a weight suspended from a pivot so that it can swing freely.[1] When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a slight degree on the amplitude, the width of the pendulum's swing. From the first scientific investigations of the pendulum around 1602 by Galileo Galilei, the regular motion of pendulums was used for timekeeping, and was the world's most accurate timekeeping technology until the ...

Radium This article is about the chemical element. For other uses, see Radium (disambiguation). Radium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) on exposure to air, forming a dull purple to blackish surface layer of radium nitride (Ra3N2). All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1600 years and decays into radon gas (specifically the isotope radon-222). When radium decays, ionizing radiation is a product, which can excite fluorescent chemicals and cause radioluminescence. Radium,  88Ra General properties Pronunciation /ˈreɪdiəm/ ​(RAY-dee-əm) Appearance silvery white metallic Mass number 226 (most stable isotope) Radium in the periodic table Hydrogen Helium Lithium Beryllium Boron Carb...

Projector For other uses, see Projector (disambiguation). Acer projector, 2012 A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Most projectors create an image by shining a light through a small transparent lens, but some newer types of projectors can project the image directly, by using lasers. A virtual retinal display, or retinal projector, is a projector that projects an image directly on the retina instead of using an external projection screen. The most common type of projector used today is called a video projector. Video projectors are digital replacements for earlier types of projectors such as slide projectors and overhead projectors. These earlier types of projectors were mostly replaced with digital video projectors throughout the 1990s and early 2000s, but old analog projectors are still used at some places. The newest types of projectors are handheld projectors that use laser...

Properties and structure A simple illustration of a non-spinning black hole The no-hair theorem states that, once it achieves a stable condition after formation, a black hole has only three independent physical properties: mass, charge, and angular momentum.[35] Any two black holes that share the same values for these properties, or parameters, are indistinguishable according to classical (i.e. non-quantum) mechanics. These properties are special because they are visible from outside a black hole. For example, a charged black hole repels other like charges just like any other charged object. Similarly, the total mass inside a sphere containing a black hole can be found by using the gravitational analog of Gauss's law, the ADM mass, far away from the black hole.[clarification needed][44] Likewise, the angular momentum can be measured from far away using frame dragging by the gravitomagnetic field.[clarification needed] When an object falls into a black hole, any information...

Yoga This article is about the umbrella term "yoga" which includes religion, philosophy, and practices. For one of the six Hindu philosophy schools, see Yoga (philosophy). For the popular yoga that explains and emphasizes the physical practices or disciplines, see Hatha yoga. For other uses, see Yoga (disambiguation). Male and female yogis from 17th- and 18th-century India Yoga (/ˈjoʊɡə/;[1] Sanskrit, योगः Listen) is a group of physical, mental, and spiritual practices or disciplines which originated in ancient India. There is a broad variety of yoga schools, practices, and goals[2] in Hinduism, Buddhism, and Jainism.[3][4][5] Among the most well-known types of yoga are Hatha yoga and Rāja yoga.[6] The origins of yoga have been speculated to date back to pre-Vedic Indian traditions; it is mentioned in the Rigveda,[note 1] but most likely developed around the sixth and fifth centuries BCE,[8] in ancient India's ascetic and śramaṇa movements.[9][note 2] The chronolo...

.Water resources A graphical distribution of the locations of water on Earth. Only 3% of the Earth's water is fresh water. Most of it is in icecaps and glaciers (69%) and groundwater (30%), while all lakes, rivers and swamps combined only account for a small fraction (0.3%) of the Earth's total freshwater reserves. Water resources are sources of water that are potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. All living things require water to grow and reproduce. 97% of the water on the Earth is salt water and only three percent is fresh water; slightly over two thirds of this is frozen in glaciers and polar ice caps.[1] The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air.[2] Fresh water is a renewable resource, yet the world's supply of groundwater is steadily decreasing, with depletion occurring most prominently in Asi...

Time For the concept in physics, see Time in physics. For the magazine, see Time (magazine). For other uses, see Time (disambiguation). The flow of sand in an hourglass can be used to measure the passage of time. It also concretely represents the present as being between the past and the future. Time is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future.[1][2][3] Time is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience.[4][5][6][7] Time is often referred to as a fourth dimension, along with three spatial dimensions.[8] Time has long been an important subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently elud...

Gas cylinder For the mechanical devices used to impart a force from a pressurized gas, see pneumatic cylinder. For the large structures used to store town gas, see gas holder. Industrial compressed gas cylinders used for oxy-fuel welding and cutting of steel. A gas cylinder or tank is a pressure vessel used to store gases at above atmospheric pressure. High-pressure gas cylinders are also called bottles, but a bottled gas may instead be in a liquid or dissolved state in the cylinder. Nomenclature differences Edit In the United States, "bottled gas" typically refers to liquefied petroleum gas. "Bottled gas" is sometimes used in medical supply, especially for portable oxygen tanks. Packaged industrial gases are frequently called "cylinder gas", though "bottled gas" is sometimes used. The United Kingdom and other parts of Europe more commonly refer to "bottled gas" when discussing any usage whether industrial, medical or liquef...

Disaster Page issues For other uses, see Disaster (disambiguation). Ruins from the 1906 San Francisco earthquake, remembered as one of the worst natural disasters in the history of the United States. A disaster is a serious disruption, occurring over a relatively short time, of the functioning of a community or a society involving widespread human, material, economic or environmental loss and impacts, which exceeds the ability of the affected community or society to cope using its own resources.[1][2] In contemporary academia, disasters are seen as the consequence of inappropriately managed risk. These risks are the product of a combination of both hazards and vulnerability. Hazards that strike in areas with low vulnerability will never become disasters, as in the case of uninhabited regions.[3] Developing countries suffer the greatest costs when a disaster hits – more than 95 percent of all deaths caused by hazards occur in developing countries, and losses due to natural haz...

The Register This article is about the technology news website. For other uses, see Register (disambiguation). The Register (nicknamed El Reg) is a British technology news and opinion website co-founded in 1994 by Mike Magee, John Lettice and Ross Alderson.[2] Situation Publishing Ltd is listed as the site's publisher. Drew Culllen is an owner, Linus Birtles the managing director and Andrew Orlowski is the Executive Editor. The Register A screenshot from August 2017 Type of site technology news Available in English Headquarters London, England, United Kingdom Owner Situation Publishing Created by Mike Magee John Lettice Slogan(s) Biting the hand that feeds IT Website www.theregister.co.uk Alexa rank 6,602 (October 2017)[1] Commercial yes Registration optional Launched 1994 Current status active History Edit The Register was founded in London as an email newsletter called Chip Connection. In 1998 The Register became a daily online news source. Ma...

Thermometer Mercury thermometer for measurement of room temperature. The application of mercury (1714) and Fahrenheit scale (1724) for liquid-in-glass thermometers ushered in a new era of accuracy and precision in thermometry.[1] A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer or the digital sensor in an infrared thermometer) in which some change occurs with a change in temperature, and (2) some means of converting this change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer or the digital readout on an infrared model). Thermometers are widely used in industry to monitor processes, in meteorology, in medicine, and in scientific research. Some of the principles of the thermometer were known to Greek philosophers of two thousand years ago. The modern thermometer gradually evolved from the th...

Electric generator This article is about electromagnetic power generation. For electrostatic generators like the Van de Graaff machine, see Electrostatic generator. U.S. NRC image of a modern steam turbine generator (STG). In electricity generation, a generator[1] is a device that converts motive power into electrical power for use in an external circuit. Sources of mechanical energy include steam turbines, gas turbines, water turbines, internal combustion engines and even hand cranks. The first electromagnetic generator, the Faraday disk, was built in 1831 by British scientist Michael Faraday. Generators provide nearly all of the power for electric power grids. The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors and generators have many similarities. Many motors can be mechanically driven to generate electricity and frequently make acceptable manual generators. Terminology Edit Early Ganz Generator in Zwevegem, West ...

Receiver Look up receive, receiver, or receivers in Wiktionary, the free dictionary. Receiver or receive may refer to: In technology Edit The listening device part of a telephone The handset that sometimes contains the above device The headset (audio) that can also contain the above device AV receiver, part of a home theater system Citrix Receiver, a software client application used for virtualization Digital media receiver Receiver (firearms), which houses the working parts of the firearm Receiver (modulated ultrasound), a device that converts a modulated ultrasonic wave into usable information Receiver (radio), an electronic device that converts a signal from a modulated radio wave into usable information Tuner (radio), a subsystem that receives radio frequency (RF) transmissions and converts into a fixed frequency Television set, "telly" (UK), is a device that combines a tuner, display, and speakers for the purpose of viewing television Tuner (televisio...

Montfort School, Yercaud Page issues Montfort School, Yercaud, is a secondary school for boys and girls (Co-ed) run by the Montfort Brothers of St. Gabriel in the town of Yercaud, near Salem in Tamil Nadu, India. The school motto is "Virtue and Labour". Montfort Higher Secondary School Location Yercaud Coordinates 11.771726°N 78.209642°E Information Type Government-aided Motto Virtue and Labour Established 1917 Founder Rev. Bro. Euguene Mary Session Single Colour(s) Blue, gold Website http://www.montfortyercaud.com/ Montfort School Statue Base The Founder Edit Rev. Bro. Eugene Mary (Julien Marie Le Pevedic) was born on May 26, 1879 at Plescop de Grand champ, in the diocese of Vannes, in Brittany. He belonged to an excellent, intelligent and educated family. While in England, he underwent a sound training in the art of conversation. In December 1905, he sailed to India with Bro. Claudien and Bro. Louis D’Anjou. Bro. Denis met them there and accomp...

Chemical reaction A thermite reaction using iron(III) oxide. The sparks flying outwards are globules of molten iron trailing smoke in their wake. A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.[1] Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions of...

Dam This article is about structures for water impoundment. For other uses, see Dam (disambiguation). Glen Canyon Dam A sideview of the Lake Vyrnwy dam, in Wales, finished in 1888 Karapuzha Dam, an earth dam in the Indian state of Kerala A small dam near Groningen, Netherlands A dam is a barrier that stops or restricts the flow of water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aquaculture, and navigability. Hydropower is often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. The word dam can be traced back to Middle English,[1] ...

Radar For other uses, see Radar (disambiguation). Long-range radar antenna, used to track space objects and ballistic missiles. Radar of the type used for detection of aircraft. It rotates steadily, sweeping the airspace with a narrow beam. Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the object(s). Radio waves (pulsed or continuous) from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed. Radar was developed secretly for military use by several nati...

Random number generation Page issues When a cubical die is rolled, a random number between 1 and 6 is obtained. Random number generation is the generation of a sequence of numbers or symbols that cannot be reasonably predicted better than by a random chance, usually through a hardware random-number generator (RNG). Various applications of randomness have led to the development of several different methods for generating random data, of which some have existed since ancient times, among whose ranks are well-known "classic" examples, including the rolling of dice, coin flipping, the shuffling of playing cards, the use of yarrow stalks (for divination) in the I Ching, as well as countless other techniques. Because of the mechanical nature of these techniques, generating large numbers of sufficiently random numbers (important in statistics) required a lot of work and/or time. Thus, results would sometimes be collected and distributed as random number tables. Nowadays, afte...

J. J. Thomson This article is about the Nobel laureate and physicist. For the moral philosopher, see Judith Jarvis Thomson. Sir Joseph John Thomson OM PRS[1] (/ˈtɒmsən/; 18 December 1856 – 30 August 1940) was an English physicist and Nobel laureate in physics, credited with the discovery and identification of the electron; and with the discovery of the first subatomic particle. Sir J. J. Thomson OM PRS Born Joseph John Thomson 18 December 1856 Cheetham Hill, Manchester, England Died 30 August 1940 (aged 83) Cambridge, England Nationality English Citizenship British Alma mater Owens College (now the University of Manchester) Trinity College, Cambridge (BA) Known for Plum pudding model Discovery of electron Discovery of isotopes Mass spectrometer invention First m/e measurement Proposed first waveguide Thomson scattering Thomson problem Coining term 'delta ray' Coining term 'epsilon radiation' Thomson (unit) Children George Paget Thomson...

Desert This article is about dry terrain. For arid climate, see Desert climate. For the act of abandoning or withdrawing support, see Desertion. For other uses, see Desert (disambiguation). Valle de la Luna ("Valley of the Moon") in the Atacama Desert of Chile, the world's driest non-polar desert[1][2][3][4] Sand dunes in the Rub' al Khali ("Empty quarter") of Saudi Arabia A desert is a barren area of landscape where little precipitation occurs and consequently living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation. About one third of the land surface of the world is arid or semi-arid. This includes much of the polar regions where little precipitation occurs and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of de...