d
\(\text { Given: } E_{\mathrm{rms}}=6 \,\mathrm{Vm}^{-1}\)

\(\frac{E_{\mathrm{rms}}}{B_{\mathrm{rms}}}=c\) or \(B_{\mathrm{rms}}=\frac{E_{\mathrm{rms}}}{c}\)

\(B_{\mathrm{rms}}=\frac{6}{3 \times 10^{8}}=2 \times 10^{-8}\, \mathrm{T}\)

since, \(B_{\mathrm{rms}}=\frac{B_{0}}{\sqrt{2}}\)

where \(B_{0}\) is the peak value of magnetic field

\(\therefore B_{0} =B_{\mathrm{rms}} \sqrt{2}=2 \times 10^{-8} \times \sqrt{2} T \)

\( B_{0}  \approx 2.83 \times 10^{-8}\, \mathrm{T}\)