What is the speed of gamma rays in vacuum?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( c \)
Gamma rays are electromagnetic waves, the shortest-wavelength band of the spectrum. In vacuum, all electromagnetic waves travel with the same speed. This speed depends only on the permeability and the permittivity of free space, and it is independent of the wavelength.
\( \displaystyle c=\frac{1}{\sqrt{\mu_0\varepsilon_0}} \)
\( c\approx3\times10^{8}\,\mathrm{m\,s^{-1}} \)
Therefore, gamma rays travel in vacuum with the speed of light, \( c \).
NCERT (2026-27):
Summary – “… Light is an electromagnetic wave; c is, therefore, also the speed of light. Electromagnetic waves other than light also have the same velocity c in free space.”