Question

An electromagnetic wave of frequency 5 GHz, is travelling in a medium whose relative electric permittivity and relative magnetic permeability both are 2. Its velocity in this medium is ________ × 10⁷ m/s.

Hint:

The refractive index of a medium is $n = \sqrt{\mu_r \epsilon_r}$. For most transparent materials, $\mu_r \approx 1$, so $n \approx \sqrt{\epsilon_r}$.

Answer 1

Correct Answer: 15

Step 1: Velocity of light in a medium is $v = \frac{c}{\sqrt{\mu_r \epsilon_r}}$.
Step 2: Given $\mu_r = 2$ and $\epsilon_r = 2$.
Step 3: $v = \frac{3 \times 10^8}{\sqrt{2 \times 2}} = \frac{3 \times 10^8}{2} = 1.5 \times 10^8$ m/s.
Step 4: $1.5 \times 10^8 = 15 \times 10^7$ m/s.