An electromagnetic wave is propagating in a medium with relative permittivity 6 and relative permeability 150. Its speed is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \( 10^{7} \) m/s
The speed of an electromagnetic wave in a medium is \( v = 1/\sqrt{\mu\varepsilon} \), which is the speed in vacuum divided by \( \sqrt{\mu_r \varepsilon_r} \).
\( \displaystyle v = \frac{c}{\sqrt{\mu_r \varepsilon_r}} = \frac{3\times10^{8}\,\mathrm{m\,s^{-1}}}{\sqrt{150 \times 6}} \)
\( \displaystyle v = \frac{3\times10^{8}\,\mathrm{m\,s^{-1}}}{30} = 10^{7}\,\mathrm{m\,s^{-1}} \)