Speed of electromagnetic wave in a medium

The speed of an electromagnetic wave in a medium is $v = \frac{c}{\sqrt{\mu_r \varepsilon_r}}$ where:

• $c = 3 \times 10^8\ \text{m/s}$
• $\mu_r = 2$
• $\varepsilon_r = 2$

Substitute the given values

$v = \frac{3 \times 10^8}{\sqrt{2 \cdot 2}}$

$v = \frac{3 \times 10^8}{\sqrt{4}} = \frac{3 \times 10^8}{2}$

$v = 1.5 \times 10^8\ \text{m/s}$

Match with the required form

The question asks for $\underline{\hspace{2cm}} \times 10^7\ \text{m/s}$

Since $1.5 \times 10^8 = 15 \times 10^7$

the required integer is $15$

Comparison with stored answer

Derived answer = $15$

Stored correct answer = $15$

Hence, the derived answer agrees with the stored answer.