decade. Research into fusion for military purposes began in the early 1940s, as part of the Manhattan Project, but was not successful until 1952. Research into controlled fusion for civilian purposes began in the 1950s, and continues to this day. What is nuclear fission? Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, often producing free neutrons and lighter nuclei, which may eventually produce photons (in the form of gamma rays). Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place). Fission is a form of nuclear transmutation because the resulting fragments are not the same element as the original atom. Nuclear fission produces energy for nuclear power and to drive the explosion of nuclear weapons.
regulated and dependent on the temperature of the external environment. In contrast, homeotherms regulate their internal body temperature by expending metabolic energy. [2][86] [157] There is a relationship between light, primary production, and ecological energy budgets. Sunlight is the primary input of energy into the planet's ecosystems. Light is composed of electromagnetic energyof different wavelengths. Radiant energy from the sun generates heat, provides photons of light measured as active energy in the chemical reactions of life, and also acts as a catalyst for genetic mutation.[2][86][157] Plants, algae, and some bacteria absorb light and assimilate the energy throughphotosynthesis. Organisms capable of assimilating energy by photosynthesis or through inorganic fixation of H2S are autotrophs. Autotrophs--responsible for primary production--assimilate light energy that becomes metabolically stored as potential energy in the form of
a large surface area is required to collect the energy at a useful rate. 8.1 Photovoltaic energy Photovoltaic energy is the conversion of sunlight into electricity. A photovoltaic cell, commonly called a solar cell or PV, is the technology used to convert solar energy directly into electrical power. A photovoltaic cell is a nonmechanical device usually made from silicon alloys. Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed. Only the absorbed photons provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material's atoms. Special treatment of the material surface
These include: Photovoltaic Systems Producing electricity directly from sunlight. Solar cells convert sunlight directly into electricity. Solar cells are often used to power calculators and watches. They are made of semiconducting materials similar to those used in computer chips. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic (PV) effect. Solar cells are typically combined into modules that hold about 40 cells; a number of these modules are mounted in PV arrays that can measure up to several meters on a side. These flat-plate PV arrays can be mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a day
rectional pin to a logic low. Sensors 71 CCDs CCDs (Charge Coupled Devices) directly convert light intensity to an electri- cal value. CCDs are used in handheld camcorders, surveillance cameras, bar code readers, imaging systems, and any other place where a representation of an image is needed. CCD Basics A CCD operates by accumulating charge on a semiconductor area. When photons fall on a CCD pixel array, the energy from the photons is absorbed by the silicon, causing an electron-hole pair to be formed. The number of electron-hole pairs is directly related to the number of photons that were absorbed, and so is directly related to the amount of light. The longer that charge is allowed to accumulate, the more electron- hole pairs will be formed. The process of allowing light to fall on a CCD array for a particular time to accumulate charge is called integration, and
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