Solid angles and polyhedral angles

A solid angle is a measure of how large an object appears to an observer looking from a specific point, but in three dimensions. It is like the 3D version of a plane angle. A polyhedral angle is formed at a point where several plane angles (faces) meet, like the corner of a cube or a pyramid.

Important properties

• Solid angles are measured in steradians (sr).

• The total solid angle around a point in space is $4\pi$ steradians.

• A polyhedral angle is defined by three or more plane angles meeting at a point (the vertex).

• The solid angle of a polyhedral angle depends on the arrangement and size of its faces.