The sunlight reaching the earth has maximum magnetic field \( 2.4\,\mu\mathrm{T} \). What is the maximum electric field in this light? Speed of light = \( 3\times10^{8}\,\mathrm{m\,s^{-1}} \)
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 720\,\mathrm{V\,m^{-1}} \)
In an electromagnetic wave the amplitudes of the electric and magnetic fields are related by \( E_0 = cB_0 \).
\( E_0 = cB_0 = 3\times10^{8}\,\mathrm{m\,s^{-1}}\times2.4\times10^{-6}\,\mathrm{T} = 720\,\mathrm{V\,m^{-1}} \)
Shortcut: Multiplying a magnetic field in \( \mu\mathrm{T} \) by \( c = 3\times10^{8} \) gives \( 300\,\mathrm{V\,m^{-1}} \) for every \( \mu\mathrm{T} \), so \( 2.4\times300 = 720\,\mathrm{V\,m^{-1}} \).