Due to presence of an em-wave whose electric component is given by ${\rm{E}} = 100\sin (\omega {\rm{t}} - {\rm{kx}}){\rm{N}}{{\rm{C}}^{ - 1}}$, a cylinder of length 200 cm holds certain amount of em-energy inside it. If another cylinder of same length but half diameter than previous one holds same amount of em-energy, the magnitude of the electric field of the corresponding em-wave should be modified as