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8.Electromagnetic waves
medium
If $c $ is the speed of electromagnetic waves in vacuum, its speed in a medium of dielectric constant $K$ and relative permeability ${\mu _r}$ is
A
$v = \frac{1}{{\sqrt {{\mu _r}K} }}$
B
$v = c\sqrt {{\mu _r}K} $
C
$v = \frac{c}{{\sqrt {{\mu _r}K} }}$
D
$v = \frac{K}{{\sqrt {{\mu _r}C} }}$
Solution
(c)Speed of light of vacuum $c = \frac{1}{{\sqrt {{\mu _0}{\varepsilon _0}} }}$ and in another medium $v = \frac{1}{{\sqrt {\mu \varepsilon } }}$
$\frac{c}{v} = \sqrt {\frac{{\mu \varepsilon }}{{{\mu _0}{\varepsilon _0}}}} = \sqrt {{\mu _r}K} $ ==> $v = \frac{c}{{\sqrt {{\mu _r}K} }}$
Standard 12
Physics
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