Let the heights be \(h\) units and \(2h\) units respectively, and the radii be \(r_1\) and \(r_2\). According to the condition, \(πr_1^2 h = πr_2^2 × 2h\) i.e., \(\cfrac{r_1^2}{r_2^2} = \cfrac{2h}{h}\) i.e., \(\cfrac{r_1}{r_2} = \sqrt{\cfrac{2}{1}} = \cfrac{\sqrt{2}}{1}\) ∴ \(r_1 : r_2 = \sqrt{2} : 1\) \(\therefore\) The ratio of the lengths of the radii of the two cylinders is \( \sqrt{2} : 1 \).