Question

The total surface area of a solid hemisphere of radius r is ------

a) 2pi r²




b) 3pi r²




c) 4pi r²


d) pi r²

​

Answer 1

Answer:

Surface area of a solid sphere with radius r is 4πr

2

A solid sphere can be divided into two equal hemispheres with a flat surface and a curved surface.

Curved surface area of a solid hemisphere will be half the surface area of solid sphere.

Hence, curved surface area of solid hemisphere =

2

1

∗4πr

2

=2πr

2

And, flat surface area of hemisphere will be the area of circle with radius r.

Hence, flat surface area of hemisphere =πr

2

Total surface area of a solid hemisphere with radius r is, S=2πr

2

+πr

2

=3πr

2