what is steradian?

3 answers

A steradian is a measure of solid angle.
Imagine that you are at the center of a hollow sphere of radius R. Now consider an area A of that sphere. Divide that area by R^2 and you have the solid angle subtended by A, in steradians.

A full sphere subtends a solid angle of 4 pi steradians, from a point inside
A steradian is a measure of solid angle.
Imagine that you are at the center of a hollow sphere of radius R. Now consider an area A of that sphere. Divide that area by R^2 and you have the solid angle subtended by A, in steradians.

A full sphere subtends a solid angle of 4 pi steradians, from a point inside
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