FACTOID # 7: The top five best educated states are all in the Northeast.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Radiation pressure

Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the energy flux density divided by the speed of light. If the radiation is totally reflected, the radiation pressure is doubled. For example, the radiation of the Sun at the Earth has an energy flux density of 1370 W/m2, so the radiation pressure is 4.6 µPa (absorbed) (see also Climate model). The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ... Electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks. ... In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. ...

Contents

Discovery

The fact that electromagnetic radiation exerts a pressure upon any surface exposed to it was deduced theoretically by James Clerk Maxwell in 1871, and proven experimentally by Lebedev in 1900[1] and by Nichols and Hull in 1901. The pressure is very feeble, but can be detected by allowing the radiation to fall upon a delicately poised vane of reflective metal (Nichols radiometer). Electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematical physicist, born in Edinburgh. ... 1871 (MDCCCLXXI) was a common year starting on Sunday (see link for calendar). ... Pyotr Nikolaevich Lebedev (Russian Пётр Николаевич Лебедев), February 24, 1866 - January 1, 1912 (new style). ... 1900 (MCM) was an exceptional common year starting on Monday of the Gregorian calendar, but a leap year starting on Saturday of the Julian calendar. ... 1901 (MCMI) was a common year starting on Tuesday (see link for calendar) of the Gregorian calendar (or a common year starting on Wednesday of the 13-day-slower Julian calendar). ... A Nichols radiometer is the apparatus used by Nichols and Hull in 1901 for the measurement of radiation pressure. ...


Theory

It may be shown by electromagnetic theory, by quantum theory, or by thermodynamics, making no assumptions as to the nature of the radiation, that the pressure against a surface exposed in a space traversed by radiation uniformly in all directions is equal to ⅓ the total radiant energy per unit volume within that space. Quantum theory is a theory of physics that uses Plancks constant. ... Thermodynamics (from the Greek thermos meaning heat and dynamics meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ...


For black body radiation, in equilibrium with the exposed surface, the energy density is, in accordance with the Stefan-Boltzmann law, equal to σT4/3c; in which σ is the Stefan-Boltzmann constant, c is the speed of light, and T is the absolute temperature of the space. One third of this energy is equal to 6.305×10−17T4 J/(m3K4), which is therefore equal to the pressure in pascals. [2] As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... In thermodynamics, a thermodynamic system is in thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, and chemical equilibrium. ... The Stefan-Boltzmann law, also known as Stefans law, states that the total energy radiated per unit surface area of a black body in unit time (known variously as the black-body irradiance, energy flux density, radiant flux, or the emissive power), j*, is directly proportional to the fourth... The Stefan-Boltzmann constant (also Stefans constant), denoted with a Greek letter σ, is a derivable physical constant, the constant of proportionality between the total energy radiated per unit surface area of a black body in unit time and the fourth power of the thermodynamic temperature, as per the... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. It is the speed of all electromagnetic radiation in a vacuum, not just visible light. ... Fig. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ...


In interplanetary space

For example, at the boiling point of water (T = 373.15 K), the pressure only amounts to 3 micropascals (about 2 pounds force per square mile). If the radiation is directional (in interplanetary space, the overwhelming proportion of the energy flux comes from the Sun alone), the radiation pressure is tripled, to σT4/c; if the body is a perfect reflector, the pressure can be doubled again, to 2σT4/c. A solar sail at the distance where the equivalent radiation temperature is the boiling point of water could thus achieve about 22 µPa, or nearly 13 lbf/sq mi. Such feeble pressures are, nevertheless, able to produce marked effects upon minute particles like gas ions and electrons, and are important in the theory of electron emission from the Sun, of cometary material, and so on (see also: Yarkovsky effect, YORP effect). Boil or furuncle is a skin disease caused by the inflammation of hair follicles, thus resulting in the localized accumulation of pus and dead tissues. ... Water is an odourless substance that is essential to all known forms of life and is known as the universal solvent. ... Concept image of a solar sail spacecraft in the process of unfurling sails. ... A gas is one of the four major phases of matter (after solid and liquid, and followed by plasma, that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss or addition of one or more electrons. ... The Electron is a fundamental subatomic particle that carries an electric charge. ... The Sun is the star of our solar system. ... A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail â€” both primarily from the effects of solar radiation upon the comets nucleus, which itself is a minor body composed of rock, dust... In physics, the Yarkovsky effect is a force felt by a body caused by the momentum carried away by the thermal photons that it emits. ... The Yarkovsky-OKeefe-Radzievskii-Paddack effect, or YORP effect for short, is a second-order variation on the Yarkovsky effect which causes a small body (such as an asteroid) to spin up or down. ...


In stellar interiors

In stellar interiors the temperatures are very high. Stellar models predict a temperature of 15 MK in the center of the Sun and at the cores of supergiant stars the temperature may exceed 1 GK. As the radiation pressure scales as the fourth power of the temperature, it becomes important at these high temperatures. In the Sun, radiation pressure is still quite small when compared to the gas pressure. In the heaviest stars, radiation pressure is the dominant pressure component. The Pleiades, an open cluster of stars in the constellation of Taurus. ... The Sun is the star of our solar system. ... Supergiants are the most massive stars. ...


Solar sails

Solar sails, a proposed method of spacecraft propulsion, would use radiation pressure from the Sun as a motive force. Private spacecraft Cosmos 1 was to have used this form of propulsion. Concept image of a solar sail spacecraft in the process of unfurling sails. ... A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. ... An artists rendering of Cosmos 1 orbiting the Earth. ...


Radiation pressure in acoustics

In acoustics, radiation pressure is the unidirectional pressure force exerted at an interface between two media due to the passage of a sound wave. Acoustics is a branch of physics and is the study of sound, mechanical waves in gases, liquids, and solids. ...


See also

The Poynting vector describes the energy flux (J·m-2·s-1) of an electromagnetic field. ...

References

  1. ^ P. Lebedev, 1901, "Untersuchungen über die Druckkräfte des Lichtes", Annalen der Physik, 1901
  2. ^ D. van Nostrand, Van Nostrand's Scientific Encyclopedia (3rd edition), D. Van Nostrand, Princeton, NJ, 1958

  Results from FactBites:
 
Radiation pressure - Wikipedia, the free encyclopedia (593 words)
Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation.
It may be shown by electromagnetic theory, by quantum theory, or by thermodynamics, making no assumptions as to the nature of the radiation, that the pressure against a surface exposed in a space traversed by radiation uniformly in all directions is equal to ⅓ the total radiant energy per unit volume within that space.
In acoustics, radiation pressure is the unidirectional pressure force exerted at an interface between two media due to the passage of a sound wave.
radiation pressure: Definition and Much More from Answers.com (845 words)
The effect is conspicuous in the case of a comet near the Sun, where the radiation pressure from the Sun forces the lighter cometary constituents away from the Sun.
The pressure is a result of the momentum carried by the radiation.
The fact that electromagnetic radiation exerts a pressure upon any surface exposed to it was deduced theoretically by James Clerk Maxwell in 1871, and proven experimentally by Lebedev in 1900 and by Nichols and Hull in 1901.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m