The speed of light in air, if an electromagnetic wave is travelling in air whose dielectric constant is $k = 1.006$, will be :

Question

$\begin {array} {1 1} (a)\;3 \times 10^8 m/s & \quad (b)\;3.88 \times 10^8 m/s \\ (c)\;2.5 \times 10^8 m/s & \quad (d)\;4.6 \times 10^8 m/s \end {array}$