Solid Angle

Covered in Section 12.3.1, the solid angle () is used in radiation intensity and is defined by the book as the region between the rays of a sphere and is measured as the ratio of the area on the sphere to the sphere's radius squared.

Equation 12.9:

Where refers to integration over the hemisphere.

The unit of the solid angle is steradian (sr), equal to radians for plane angles?

14A - 2nd Class