A radio wave of frequency 90 MHz enters a ferrite rod. If $ε_r = 10^3$ and $\mu_r = 10$, then the velocity and wavelength of the wave in ferrite are
Answer & explanation
Correct answer: option 2
Refractive Index is $ n = \sqrt{\mu_r \epsilon_r} = \sqrt{10^4} = 100$
Velocity in ferrite is $V_{ferrite}=\frac{c}{\sqrt{\mu_rε_r}}=\frac{3×10^8}{\sqrt{10×10^{3}}}=3×10^6 ms^{-1}$
Wavelength in ferrite $λ_{ferrite}=\frac{V_{ferrite}}{\nu}=\frac{3×10^6}{90×10^6}=3.33 × 10^{-2} \, m$