Speed of the Radiowaves, Gamma rays, X-rays and Microwaves are represented by \( V_R, V_G, V_X \) and \( V_M \) respectively in free space. Which option is correct?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \( V_R=V_G=V_X=V_M \)
All electromagnetic waves, whatever their wavelength or frequency, travel through free space at the same speed, \( c = 1/\sqrt{\mu_0\varepsilon_0} = 3\times10^{8}\,\mathrm{m\,s^{-1}} \). Radio waves, microwaves, X-rays and gamma rays differ in frequency and wavelength (\( c = \nu\lambda \)), not in speed.
NCERT (2026-27):
Points to Ponder – “… The basic difference between various types of electromagnetic waves lies in their wavelengths or frequencies since all of them travel through vacuum with the same speed. Consequently, the waves differ considerably in their mode of interaction with matter.”