A hollow sphere is what is left of a sphere with radius \(r_{\scriptsize{2}}\), when a sphere with radius \(r_{\scriptsize{1}}\) has been removed from it, the two spheres having the same centre and \(r_{\scriptsize{1}}\) < \(r_{\scriptsize{2}}\).
Formulas
The volume V of a hollow ball is:
\(V = \dfrac{4\pi (r_{\scriptsize{2}}^3~ – ~r_{\scriptsize{1}}^3)}{3}\)