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International System of Units (view source)
Revision as of 15:45, May 16, 2007
, 15:45, May 16, 2007no edit summary
=== Steradian ===
=== Steradian ===
The '''steradian''' (symbol sr) is the ''solid angle'' unit. A ''solid angle'' is actually one [[nappe]] of a right circular conical surface. One steradian is the measure of a solid angle that subtends a portion of the surface of a [[sphere]] having an area equal to that of a square having sides equal in length to the radius. By convention, the [[surface area]] of a sphere is 4πr<sup>2</sup>, where r is the length of the radius, and thus the maximum "major solid angle" of any sphere is 4π steradians.
The '''steradian''' (symbol sr) is the ''solid angle'' unit. A ''solid angle'' is actually one [[nappe]] of a right circular conical surface. One steradian is the measure of a solid angle that subtends a portion of the surface of a [[sphere]] having an area equal to that of a square having sides equal in length to the radius. By convention, the [[surface area]] of a sphere is 4πr<sup>2</sup>, where r is the length of the radius, and thus the maximum "major solid angle" of any sphere is 4π steradians.
==Obsolete metric units==
==Obsolete metric units==