In a plane electromagnetic wave propagating in vacuum, the electric field oscillates sinusoidally at a frequency of 5.0 × 1010 Hz. The wavelength of the wave is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 6 × 10−3 m
All electromagnetic waves travel in vacuum with speed \( c = 3\times10^{8}\,\mathrm{m\,s^{-1}} \), and the wavelength is related to the frequency of oscillation of the fields by \( c = \nu\lambda \).
\( \displaystyle \lambda = \frac{c}{\nu} \)
\( \displaystyle \lambda = \frac{3\times10^{8}\,\mathrm{m\,s^{-1}}}{5.0\times10^{10}\,\mathrm{Hz}} \)
\( \lambda = 6\times10^{-3}\,\mathrm{m} \)
A wavelength of 6 mm lies in the microwave region.
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 – …
