The magnetic field in a travelling electromagnetic wave has a peak value of 30 nT. The peak value of electric field strength is: (speed of light in free space is \( 3\times10^{8}\,\mathrm{m/s} \)).
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 9.0 V/m
In an electromagnetic wave in free space the peak fields are related by the speed of light, \( E_0 = cB_0 \).
\( B_0 = 30\,\mathrm{nT} = 30\times10^{-9}\,\mathrm{T} \)
\( E_0 = cB_0 = 3\times10^{8}\times30\times10^{-9} = 9\,\mathrm{V\,m^{-1}} \)
Note: NTA picked this question from an NCERT (2026-27) exercise and changed the figures. Do not ignore NCERT while practising numericals.
NCERT (2026-27):
Exercises – …
