The velocity of an electromagnetic wave in a medium is `2xx10^(8) mS^(-1)` . If the relative permeability is 1 the relative permittivity of the medium is `(C_(0)=3xx10^(8) mS^(-1))`

Options

A. `1.0`
B. `1.8`
C. `2.5`
D. `1.2`

Answer

B

Explanation

Speed of an electromagnetic wave in vacuum is `c=(1)/(sqrt(mu_(0)epsilon_(0)))`
Speed of an electromagnetic wave in a medium is `v-(1)/(sqrt(muepsilon))`
`(v)/(c)=(sqrt(mu_(0)epsilon_(0)))/(sqrt(muepsilon))=(1)/(sqrt(mu_(r)epsilon_(r)))" "[because mu_(r)=(mu)/(mu_(0)), epsilon_(r)=(epsilon)/(epsilon_(0))]`
`(2.5xx10^(8))/(3xx10^(8))=(1)/(sqrt(0.8xxepsilon_(r)))" or "epsilon_(r)=(3xx3)/(0.8xx2.5xx2.5)=1.8`