Question

The total surface area of a hemisphere having radius r is _____ .

• A. $4\pi r^2$
• B. $3\pi r^2$
• C. $2\pi r^2$
• D. $\frac{5}{2}\left(\pi r^2\right)$

Answer 1

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


We know that, surface area of a sphere of radius r is $4\pi r^2$.
Hence, the curved surface area of the hemisphere is $2\pi r^2$.
The area of the flat circular surface of radius r is $\pi r^2$.

Hence, the total surface area of the hemisphere
$=2\pi r^2+\pi r^2=3\pi r^2$