Electromagnetic Waves Ques 9
9. If $\varepsilon_0$ and $\mu_0$ are the electric permittivity and magnetic permeability in vacuum, $\varepsilon$ and $\mu$ are corresponding quantities in medium, then refractive index of the medium is
[1997]
(a) $\sqrt{\frac{\varepsilon}{\varepsilon_0}}$
(b) $\sqrt{\frac{\varepsilon_0 \mu}{\varepsilon \mu_0}}$
(c) $\sqrt{\frac{\varepsilon_0 \mu_0}{\varepsilon \mu}}$
(d) $\sqrt{\frac{\varepsilon \mu}{\varepsilon_0 \mu_0}}$
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Answer:
Correct Answer: 9.(d)
Solution:
- (d) We know that velocity of electromagnetic wave in vacuum
$(v_0)=\frac{1}{\sqrt{\mu_0 \varepsilon_0}}$ and velocity of
electromagnetic wave in medium is
$(v)=\frac{1}{\sqrt{\mu \varepsilon}}$.
Therefore refractive index of the medium
$(\mu)=\frac{\text{ Vel. of E.M. wave in vacuum }(v_0)}{\text{ Vel. of E.M. wave in medium }(v)}$
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