Question

How to find a solid angle?

Answer 1

Solid Angle:

1. A solid angle is defined as a three-dimensional angle.
2. It is the angle subtended by any part of a spherical surface of unit radius at its center.
3. It is represented as $\Omega$.
4. A solid angle is a dimensionless quantity.
5. The SI unit of solid angle is steradian.
6. Formula to find the solid angle is, if $A$ is the area of a part of the spherical surface, and $r$ is the radius of the sphere, then the solid angle is given as

$\begin{array}{l}\Omega =\frac{A}{(r{)}^2}\end{array}$