c
Given : Frequency of wave \(f =5 GHz\)

\(=5 \times 10^{9} Hz\)

Relative permittivity, \(\epsilon_{ r }=2\)

and Relative permeability, \(\mu_{ r }=2\)

Since speed of light in a medium is given by,

\(v =\frac{1}{\sqrt{\mu \in}}=\frac{1}{\sqrt{\mu_{ s } \mu_{0} \cdot \epsilon_{ s } \epsilon_{0}}}\)

\(v =\frac{1}{\sqrt{\mu_{ s } \epsilon_{ x }}} \frac{1}{\sqrt{\mu_{0} \epsilon_{0}}}=\frac{ C }{\sqrt{\mu_{ s } \epsilon_{ r }}}\)

Where \(C\) is speed of light is vacuum.

\(\therefore v =\frac{3 \times 10^{8}}{\sqrt{4}}=\frac{30 \times 10^{7}}{2} m / s\)

\(=15 \times 10^{7} m / s\)

\(\therefore\) Ans. is \(15\)