# The speed of electromagnetic wave in a medium of dielectric constant 2.25 and relative permittivity 4 is

Q: The speed of electromagnetic wave in a medium of dielectric constant 2.25 and relative permittivity 4 is

(a) 1 × 108 m/s

(b) 2.5 × 108 m/s

(c) 2 × 108 m/s

(d) 1.5 × 108 m/s

Sol: $\large c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}$

$\large v = \frac{1}{\sqrt{\mu_0 \mu_r \epsilon_0 \epsilon_r}}$

$\large v = \frac{c}{\sqrt{\mu_r \epsilon_r}}$

$\large v = \frac{3 \times 10^8}{\sqrt{4 \times 2.25}}$

v = 1 × 108 m/s