The solid angle subtended by a part of a spherical surface at the centre of the sphere is a suppleme

Question

The solid angle subtended by a part of a spherical surface at the centre of the sphere is a supplementary quantity. Its SI unit and dimensional formula are respectively:

Professor PC Thomas Classes · Answer

The SI unit of solid angle is the steradian (sr). Since it is defined as the ratio of area to the square of the radius ($dA/r^2$), its dimensional formula is $[L^2]/[L^2] = [L^0 M^0 T^0]$, making it a dimensionless quantity.