Question

The total surface area of a hemisphere of radius r is given by

• A. $2\pi r^2$
• B. $\pi r^2$
• C. $3\pi r^2$
• D. $4\pi r^2$

Answer 1

The correct option is C $3\pi r^2$

The surface area of a sphere of radius r is $4\pi r^2$. Half of this is $2\pi r^2$.

If you have a hemispherical object then it has a base which is a circle of radius r.

The area of a circle of radius r is $\pi r^2$ and thus if the hemisphere is meant to include the base then the surface area is $2\pi r^2+\pi r^2=3\pi r^2$.