A place electromagnetic wave
`F_(s)=100 cos(6xx10^(8)t+4x) V//m`
Propagates in a medium of dielectric constant. The refractive index is

Options

A. 1.5
B. `2.0`
C. 2.4
D. `4.0`

Answer

B

Explanation

Comparing the givne equation with the equation of plane electromagnetic wave, we get
`E_(z)=E_(0)cos(omegat+kx) therefore omega=6xx10^(8) and k = 4`
Velocity of light in medium,
`v=(omega)/(k)=(6xx10^(8))/(4)=(3)/(2)xx10^(8)m//s`
Fefractive index, `mu=(c)/(v)=(3xx10^(8))/((3//2)xx10^(8))=2`