Question 15

Electromagnetic waves travel in a medium with speed of $$1.5 \times 10^8 \text{ m s}^{-1}$$. The relative permeability of the medium is 2.0. The relative permittivity will be:

Solution

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$$v = \frac{c}{\sqrt{\mu_r \epsilon_r}}$$. Given $$v = 1.5 \times 10^8$$ m/s, $$\mu_r = 2$$.

$$\frac{c}{v} = \sqrt{\mu_r \epsilon_r} \Rightarrow \left(\frac{3 \times 10^8}{1.5 \times 10^8}\right)^2 = \mu_r \epsilon_r \Rightarrow 4 = 2\epsilon_r \Rightarrow \epsilon_r = 2$$.

The correct answer is Option (1): 2.

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