Solution

Plane angle $= \frac{arc}{radius}$ and solid angle $= \frac{area}{r^2}$ are ratios of like quantities, so they are dimensionless. However, they have units: radian (rad) and steradian (sr) respectively. So they have units but no dimensions.

Concept plane and solid angle

Units and Measurements in past papers

53 questions from this chapter have appeared across 25 exam years.