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Home  >>  JEEMAIN and AIPMT  >>  Physics  >>  Class12  >>  Electromagnetic Waves
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Electromagnetic waves travel in a medium at a speed of $2 \times 10^8 m/s$. The relative permeability of the medium is $1$. Calculate the relative permittivity.

$\begin {array} {1 1} (a)\;2.25 & \quad (b)\;22.5 \\ (c)\;225 & \quad (d)\;0.225 \end {array}$

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$v = \large\frac{1}{\sqrt{ \mu \in}}$$ = \large\frac{1}{\sqrt{( \mu_o \mu_r \in_ o \in_r )}}$
$= \large\frac{c}{ \sqrt{\mu_r \in_r}}$
$ \Rightarrow v^2 = \large\frac{2}{ \mu_r \in_r} $
$ \Rightarrow \in_r = \large\frac {c^2}{\mu_rv^2}$$ =\large\frac{ (3 \times 10^8 )^2 }{(2 \times 10^8 )^2} $$= 2.25$
Ans : (a)

 

answered Mar 4, 2014 by thanvigandhi_1
edited Oct 8, 2014 by thagee.vedartham
 

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