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Topic: Steradian

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Solid angle

Radian

Angle excess

Intensity

Radiant intensity

Photometry (optics)

Lumen (unit)

Candlepower

Candela

Luminous efficacy

Lux

Luminous flux

SI

Luminous intensity

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	Steradian - Wikipedia, the free encyclopedia
		The steradian (symbol: sr) is the SI unit of solid angle.
		The steradian is the 3 dimensional equivalent of the 2 dimensional radian.
		The steradian is defined as "the solid angle subtended at the center of a sphere of radius r by a portion of the surface of the sphere having an area r
	en.wikipedia.org /wiki/Steradian (218 words)

	Steradian (Site not responding. Last check: 2007-11-07)
		The steradian (ste from Greek stereos, solid) is the SI derived unit of solid angle, and the 3-dimensional equivalent of the radian.
		The steradian is defined as "the solid angle subtended at the center of a sphere of radius r by a portion ofthe surface of the sphere having an area r
		A steradian also equal to the spherical area of a polygon having an angle excess of 1 radian, to 1/4 π of acomplete sphere, or to 57.2957795 degrees squared.
	www.therfcc.org /steradian-118666.html (183 words)

	SQUARE ONE : Quantitative Concepts (Site not responding. Last check: 2007-11-07)
		A steradian is defined as the solid angle which, from the centre of a sphere, cuts off an area of the surface of that sphere equal to the square of its radius.
		steradians (as the equation for the surface area of a sphere is 4
		As 1 steradian has a projected area of 1 square meter at a distance of 1 meter, a 1 candela (1 lm/sr) light source will similarly produce 1 lumen per square foot at a distance of 1 foot, and 1 lumen per square meter at 1 meter.
	www.squ1.com /light/quantities.html (1161 words)

	How is the 'STERADIAN' defined and how is it used?
		Steradians are a measure of the angular 'area' subtended by a two dimensional surface about the origin in three dimensional space, just as a radian is a measure of the angle subtended by a one dimensional line about the origin in two dimensional (plane) space.
		Numerically, the number of steradians in a sphere is equal to the surface area of a sphere of unit radius.
		Not surprisingly, steradians find heavy use in antenna engineering to characterize such properties as the 'directivity' of an antenna relative to an 'isotropic' radiator (one that radiates uniformly in all directions through the surface of an imaginary sphere).
	www.physlink.com /Education/AskExperts/ae174.cfm (357 words)

	Steradian
		The steradian (ste from Greek stereos, solid) is the SI supplementary unit of solid angle.
		It is also equal to the spherical area of a polygon having an angle excess of 1 radian.
		There are 4π steradians in a complete sphere.
	www.ebroadcast.com.au /lookup/encyclopedia/st/Steradian.html (91 words)

	Steradian (Site not responding. Last check: 2007-11-07)
		"Steradian" is a common misspelling or typo for: serration, steadied, steadying, steroidal, strain, striding.
		The steradian is the solid angle which has its apex at the centre of a sphere and which describes on the surface of the sphere an area equal to that of a square having as its side the radius of the sphere.
		The solid angle which, having its vertex in the centre of a sphere, cuts off an area on the surface of the sphere equal to that of a square having sides of length equal of the radius of the sphere.
	www.websters-online-dictionary.org /st/steradian.html (518 words)

	PHOTOMETRIC TERMS - A SUMMARY (Site not responding. Last check: 2007-11-07)
		Steradian = solid angle with area r² at a radius of r from the apex.
		Since the area of a sphere = 4(Pi)r², the area subtended by the steradian is 1/(4(Pi)) of the area of the sphere.
		Since 100 candles is 100 lumens/steradian, and one steradian for this sphere has an area of 20cm x 20cm = 400 cm², the area in question is 240/400=0.6 steradians, and the number of lumens passing through is 0.6 x 100 = 60 lumens.
	vsg.cape.com /~pbaum/flux.htm (262 words)

	* Steradian - (GIS): Definition (Site not responding. Last check: 2007-11-07)
		A steradian is the solid (3D) angle formed when an area on the surface of a sphere is equal to the square of the radius of the sphere.
		There are 4 Pi steradians in a sphere...
		The notion of radiant intensity is given by the radiant flux per unit of solid angle ω (in steradians - a cone angle in which the unit is a radian or 57 degrees, 17 minutes, 44 seconds); this diagram may help to visualize this...
	www.bestknows.com /gis/steradian.html (80 words)

	NIST Guide to SI Units - Appendix A. Definitions of the SI Base Units and the Radian and Steradian (Site not responding. Last check: 2007-11-07)
		[3]; the definitions of the SI supplementary units, the radian and steradian, which are now interpreted as SI derived units (see Sec.
		The radian is the plane angle between two radii of a circle that cut off on the circumference an arc equal in length to the radius.
		The steradian is the solid angle that, having its vertex in the center of a sphere, cuts off an area of the surface of the sphere equal to that of a square with sides of length equal to the radius of the sphere.
	physics.nist.gov /Pubs/SP811/appenA.html (414 words)

	Encyclopedia: Steradian (Site not responding. Last check: 2007-11-07)
		In mathematics and physics, the radian is a unit of angle measure.
		A solid angle is the three dimensional analog of the ordinary angle.
		Until 1995, SI (International System of Units) supplementary units were: As of October 1995, the category of supplementary units has been abolished from the SI system of measurement, and the radian and the steradian are now considered SI derived units.
	www.nationmaster.com /encyclopedia/Steradian (516 words)

	steradian - a Whatis.com definition (Site not responding. Last check: 2007-11-07)
		The steradian (symbolized sr) is the Standard International (SI) unit of solid angular measure.
		A steradian is defined as conical in shape, as shown in the illustration.
		Imagine a cone with its apex P at the center of the sphere, and that intersects the surface in a circle (shown as a red ellipse, the upper half of which is dashed).
	whatis.techtarget.com /definition/0,,sid9_gci528813,00.html (295 words)

	Candela
		The strange choice of the number 683 is to make the value identical to that obtained with the previous version of the unit: the emission from 1 square centimeter of glowing, solidifying platinum.
		The steradian is the cone of light spreading out from the source which would illuminate one square meter of the inner surface of a sphere of 1 m radius around the source.
		One steradian covers one square meter on the surface of a globe of 1 meter radius.
	www.electro-optical.com /whitepapers/candela.htm (1466 words)

	luminous intensity - a Whatis.com definition (Site not responding. Last check: 2007-11-07)
		Luminous intensity is an expression of the amount of light power emanating from a point source within a solid angle of one steradian.
		A frequency of 540 THz corresponds to a wavelength of about 555 nanometers (nm), which is in the middle of the visible-light spectrum, and is generally accepted as the frequency and wavelength at which the average human eye is most sensitive.
		A steradian is the standard unit solid angle; a sphere encloses 4
	searchwebservices.techtarget.com /gDefinition/0,294236,sid44_gci553541,00.html (267 words)

	watt per steradian - a Whatis.com definition (Site not responding. Last check: 2007-11-07)
		steradians in three-dimensional space with respect to a point of reference.
		The watt per steradian can be used to define the radiant intensity at any EM wavelength, from low-frequency radio waves through the gamma-ray spectrum.
		Suppose an electromagnetic field having P watts of total power is radiated from an isotropic emitter (that is, a point source that radiates equally well in all directions).
	whatis.techtarget.com /gDefinition/0,294236,sid44_gci547182,00.html (205 words)

	NIST Guide to SI Units - 4 The Three Classes of SI Units and the SI Prefixes
		4.3, the radian and steradian, which are the two supplementary units, are included in Table 3a.
		The steradian (sr) is not an SI base unit.
		As previously stated, there are two units in this class: the radian, symbol rad, the SI unit of the quantity plane angle; and the steradian, symbol sr, the SI unit of the quantity solid angle.
	physics.nist.gov /Pubs/SP811/sec04.html (1301 words)

	Sunrise Instruments, LLC • Light Measurment Specialists (Site not responding. Last check: 2007-11-07)
		The radiometric unit is watts per steradian”; the photopic unit is the candela”;.
		The unit is “lumens per square meter per steradian” or, equivalently, candela per square meter”.
		A solid angle of one steradian from a point is formed by a [symmetrical or irregularly shaped] cone radiating from the point that intersects an area equal to the square of the radius on a sphere centered at the point.
	www.sunriseinstruments.com /terminology.html (942 words)

	steradian (Site not responding. Last check: 2007-11-07)
		In SI, the unit of solid angle, equal to the solid angle which cuts off, on the surface of a sphere, an area equal to the area of a square whose sides are the same length as the radius of the sphere.
		The entire surface of a sphere subtends 4π steradians.
		One steradian is approximately equal to 3,283 square degrees or 1.18 × 10
	www.sizes.com /units/steradian.htm (72 words)

	Steradian : Sr
		Steradian : Sr The steradian (ste from Greek stereos, solid) is the SI supplementary unit of solid angle.
		WILDING, esp. fruit of wild apple or crab tree (Webster).
		All is still licensed under the GNU FDL.
	www.wordlookup.net /sr/sr.html (131 words)

	StereoTimes -- Legacy Audio Whisper Loudspeakers (Site not responding. Last check: 2007-11-07)
		The Steradian vs. the Z-Systems for Low Frequency EQ "…while I know I am missing some of the smallest details, I will not be removing the Steradian from the signal path again any time soon since the benefits of using it with the Whispers far outweigh the downside, to my ears."
		Several reviews have opined that the Steradian is not an acoustically transparent device or is not worthy of the inherent capabilities of the Whisper.
		Results: The Steradian does in fact mask some very low level detail in a way which, while allowing you to hear the detail as a sonic event, does not allow you to hear as clearly what that event was.
	www.stereotimes.com /speak040300.shtm (4825 words)

	The 4pi Steradian image (Site not responding. Last check: 2007-11-07)
		A 4pi Steradian image is an oval or circular shaped 2-dimensional (flat) image representing the full 360 x 180° 3-D sphere.
		The term Steradian is the “Standard International Unit” of solid angular measure.
		Just as there are 360 degrees or 2pi radians in a circle, there are 4pi Steradians in a sphere.
	360vr.com /4pi/4pi.html (287 words)

	Steradian - Encyclopedia, History, Geography and Biography
		The steradian was formerly an SI supplementary unit, but this category was abolished from the SI system in 1995.
		This page was last modified 23:18, 3 Jun 2005.
		The article about Steradian contains information related to Steradian.
	www.arikah.com /encyclopedia/Steradian (164 words)

	Steradian Encyclopedia Article, Definition, History, Biography (Site not responding. Last check: 2007-11-07)
		Looking For steradian - Find steradian and more at Lycos Search.
		Find steradian - Your relevant result is a click away!
		Look for steradian - Find steradian at one of the best sites the Internet has to offer!
	www.karr.net /search/encyclopedia/Steradian (357 words)

	Solid Angle \| Steradian
		The maximum solid angle is ~12.57, corresponding to the full area of the unit sphere, which is 4*Pi.
		Standard unit of a solid angle is the Steradian (sr).
		A book often used in university geometry classes, which explains all topics in a well organized manner.
	www.schorsch.com /kbase/glossary/solid_angle.html (226 words)

	MSN Encarta - Dictionary - steradian
		Search for "steradian" in all of MSN Encarta
		SI measurement of solid angle: the basic International System unit of measurement of a solid angle in a sphere.
		One steradian is the solid angle made at the center of a sphere by an area on the surface of the sphere equal to the square of the sphere's radius.
	encarta.msn.com /dictionary_1861714922/steradian.html (87 words)

	steradian concept from the Astronomy knowledge base (Site not responding. Last check: 2007-11-07)
		Next named derived SI unit: tesla Up: named derived SI unit, solid angle unit Previous named derived SI unit: sievert
		One steradian is equal to the angle subtended at the centre of a sphere by an area of surface equal to the square of the radius.
		The surface of a sphere subtends an angle of 4π steradians at its centre.
	www.site.uottawa.ca:4321 /astronomy/steradian.html (111 words)

	Outdoor Laser Tag - Steradian Technologies (Site not responding. Last check: 2007-11-07)
		This exciting new field sport has all the excitement of other shooting and hunting sports without the danger.
		Outdoor Laser Tag is sweeping the globe, and Steradian Technologies is leading the way with the longest range guns,
		And since all we shoot is a beam of invisible infrared light, no protective clothing is needed!
	www.steradiantech.com (107 words)

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