HOME  TheInfoList.com 
Radiation Pressure Radiation pressure Radiation pressure is the pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength which is absorbed, reflected, or otherwise emitted (e.g. black body radiation) by matter on any scale (from macroscopic objects to dust particles to gas molecules). The forces generated by radiation pressure are generally too small to be noticed under everyday circumstances, however they are important in some physical processes. This particularly includes objects in outer space where it is usually the main force acting on objects besides gravity, and where the net effect of a tiny force may have a large cumulative effect over long periods of time [...More...] 


Pressure Pressure Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure Gauge pressure (also spelled gage pressure)[a] is the pressure relative to the ambient pressure. Various units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the SI unit SI unit of pressure, the pascal (Pa), for example, is one newton per square metre; similarly, the poundforce per square inch (psi) is the traditional unit of pressure in the imperial and US customary systems. Pressure may also be expressed in terms of standard atmospheric pressure; the atmosphere (atm) is equal to this pressure, and the torr is defined as 1⁄760 of this [...More...] 


Solar System The Solar System[a] is the gravitationally bound system comprising the Sun Sun and the objects that orbit it, either directly or indirectly.[b] Of those objects that orbit the Sun Sun directly, the largest eight are the planets,[c] with the remainder being smaller objects, such as dwarf planets and small Solar System Solar System bodies. Of the objects that orbit the Sun Sun indirectly, the moons, two are larger than the smallest planet, Mercury.[d] The Solar System Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with the majority of the remaining mass contained in Jupiter. The four smaller inner planets, Mercury, Venus, Earth Earth and Mars, are terrestrial planets, being primarily composed of rock and metal [...More...] 


Irradiance In radiometry, irradiance is the radiant flux (power) received by a surface per unit area. The SI unit of irradiance is the watt per square metre (W/m2). The CGS unit erg per square centimetre per second (erg·cm−2·s−1) is often used in astronomy. Irradiance is often called intensity because it has the same physical dimensions, but this term is avoided in radiometry where such usage leads to confusion with radiant intensity. Spectral irradiance is the irradiance of a surface per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength [...More...] 


Diffuse Reflection Diffuse reflection Diffuse reflection is the reflection of light or other waves or particles from a surface such that a ray incident on the surface is scattered at many angles rather than at just one angle as in the case of specular reflection. An ideal diffuse reflecting surface is said to exhibit Lambertian reflection, meaning that there is equal luminance when viewed from all directions lying in the halfspace adjacent to the surface. A surface built from a nonabsorbing powder such as plaster, or from fibers such as paper, or from a polycrystalline material such as white marble, reflects light diffusely with great efficiency [...More...] 


Stefan–Boltzmann Law The Stefan–Boltzmann law Stefan–Boltzmann law describes the power radiated from a black body in terms of its temperature. Specifically, the Stefan–Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time j ⋆ displaystyle j^ star (also known as the blackbody radiant emittance) is directly proportional to the fourth power of the black body's thermodynamic temperature T: j ⋆ = σ T 4 . displaystyle j^ star =sigma T^ 4 . The constant of proportionality σ, called the Stefan–Boltzmann constant derives from other known physical constants [...More...] 


Wave–particle Duality Wave–particle duality Wave–particle duality is the concept in quantum mechanics that every particle or quantic entity may be partly described in terms not only of particles, but also of waves. It expresses the inability of the classical concepts "particle" or "wave" to fully describe the behavior of quantumscale objects. As Albert Einstein Albert Einstein wrote:[1]It seems as though we must use sometimes the one theory and sometimes the other, while at times we may use either. We are faced with a new kind of difficulty [...More...] 


Planck's Constant The Planck constant Planck constant (denoted h, also called Planck's constant) is a physical constant that is the quantum of action, central in quantum mechanics. First recognized in 1900 by Max Planck, it was conceived as the proportionality constant between the minimal increment of energy, E, of a hypothetical electrically charged oscillator in a cavity that contained black body radiation, and the frequency, f, of its associated electromagnetic wave. In 1905, the value E, the minimal energy increment of a hypothetical oscillator, was theoretically associated by Albert Einstein Albert Einstein with a "quantum" or minimal element of the energy of the electromagnetic wave itself. The light quantum behaved in some respects as an electrically neutral particle, as opposed to an electromagnetic wave [...More...] 


Thermal Equilibrium Two physical systems are in thermal equilibrium if no heat flows between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics. A system is said to be in thermal equilibrium with itself if the temperature within the system is spatially and temporally uniform. Systems in thermodynamic equilibrium are always in thermal equilibrium, but the converse is not always true [...More...] 


Planck Law Planck's law Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. The law is named after Max Planck, who proposed it in 1900. It is a pioneering result of modern physics and quantum theory. The spectral radiance of a body, Bν, describes the amount of energy it gives off as radiation of different frequencies. It is measured in terms of the power emitted per unit area of the body, per unit solid angle that the radiation is measured over, per unit frequency [...More...] 


Stefan–Boltzmann Constant The Stefan– Boltzmann constant Boltzmann constant (also Stefan's constant), a physical constant denoted by the Greek letter σ (sigma), is the constant of proportionality in the Stefan–Boltzmann law: "the total intensity radiated over all wavelengths increases as the temperature increases", of a black body which is proportional to the fourth power of the thermodynamic temperature.[1] The theory of thermal radiation lays down the theory of quantum mechanics, by using physics to relate to molecular, atomic and subatomic levels [...More...] 


Kelvins The Kelvin Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The kelvin (symbol: K) is the base unit of temperature in the International System of Units International System of Units (SI). The kelvin is defined as the fraction 1⁄273.16 of the thermodynamic temperature of the triple point of water (exactly 0.01 °C or 32.018 °F).[1] In other words, it is defined such that the triple point of water is exactly 273.16 K. The Kelvin Kelvin scale is named after the Belfastborn, Glasgow University engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale". Unlike the degree Fahrenheit Fahrenheit and degree Celsius, the kelvin is not referred to or typeset as a degree [...More...] 


Astronomical Unit The astronomical unit (symbol: au,[1][2][3] ua,[4] or AU) is a unit of length, roughly the distance from Earth Earth to the Sun. However, that distance varies as Earth Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year. Originally conceived as the average of Earth's aphelion and perihelion, it was defined exactly as 7011149597870700000♠149597870700 metres or about 150 million kilometres (93 million miles) since 2012.[5] The astronomical unit is used primarily for measuring distances within the Solar System Solar System or around other stars [...More...] 


Momentum In Newtonian mechanics, linear momentum, translational momentum, or simply momentum (pl. momenta) is the product of the mass and velocity of an object. It can be more generally stated as a measure of how hard it is to stop a moving object. It is a threedimensional vector quantity, possessing a magnitude and a direction. If m is an object's mass and v is the velocity (also a vector), then the momentum is p = m v , displaystyle mathbf p =mmathbf v , In SI units, it is measured in kilogram meters per second (kg⋅m/s). Newton's second law Newton's second law of motion states that a body's rate of change in momentum is equal to the net force acting on it. Momentum Momentum depends on the frame of reference, but in any inertial frame it is a conserved quantity, meaning that if a closed system is not affected by external forces, its total linear momentum does not change [...More...] 


Watt The watt (symbol: W) is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second,[1] and is used to quantify the rate of energy transfer [...More...] 


Metre The metre (British spelling and BIPM spelling[1]) or meter (American spelling) (from the French unit mètre, from the Greek noun μέτρον, "measure") is the base unit of length in some metric systems, including the International System of Units International System of Units (SI). The SI unit symbol is m.[2] The metre is defined as the length of the path travelled by light in a vacuum in 1/299 792 458 second.[1] The metre was originally defined in 1793 as one tenmillionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a prototype metre bar (the actual bar used was changed in 1889). In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton86. In 1983, the current definition was adopted. The imperial inch is defined as 0.0254 metres (2.54 centimetres or 25.4 millimetres). One metre is about 3 3⁄8 inches longer than a yard, i.e [...More...] 
