Two electromagnetic waves have the frequencies as \( 4\times10^{14}\,\mathrm{Hz} \) and \( 8\times10^{14}\,\mathrm{Hz} \). The ratio of their speeds in air is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 1 : 1
All electromagnetic waves travel with the same speed in vacuum, \( c = 3\times10^{8}\,\mathrm{m\,s^{-1}} \), whatever their frequency, and in air the speed is practically the same. A different frequency only changes the wavelength, through \( c = \nu\lambda \).
So the ratio of their speeds is 1 : 1.
NCERT (2026-27):
Nature of Electromagnetic Waves – “… The velocity of electromagnetic waves in free space or vacuum is an important fundamental constant. It has been shown by experiments on electromagnetic waves of different wavelengths that this velocity is the same (independent of wavelength) to within a few metres per second, out of a value of 3 × 108 m/s.”