A plane electromagnetic wave, has frequency of 2.0 $\times$ 1010 Hz and its energy density is 1.02 $\times$ 10–8 J/m3 in vacuum. The amplitude of the magnetic field of the wave is close to ( $${1 \over {4\pi {\varepsilon _0}}} = 9 \times {10^9}{{N{m^2}} \over {{C^2}}}$$ and speed of light = 3 $\times$ 108 ms–1)