Q. The dielectric constant of air is 1.006. The speed of Electromagnetic Wave travelling in air is $a\ \times \ 10^{8}$ ms$^{-1}$, where $a\ $is about
A) 3
B) 3.88
C) 2.5
D) 3.2
Explanation
(a) For an Electromagnetic Wave (in vacuum),
Velocity $c = \ \frac{1}{\sqrt{\mu_{0}\varepsilon_{0}}}\ = \ 3\ \times \ 10^{8}\ {ms}^{- 1}$
Air acts almost as vacuum, hence
$a = 3(approx)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.