Question

A plane electromagnetic wave $E_z=100\cos \left(6\times 10^{8}t+4x\right)V/m$ propagates in a medium. The refractive index of the medium is

• A. 1.5
• B. 2.0
• C. 2.4
• D. 4.0

Answer 1

Answer: (B)

Comparing the given equation with the equation of plane electromagnetic wave, we get
$E_z=E_0\cos (\omega t+kx)\therefore \omega =6\times 10^8$ and $k=4$
Velocity of light in medium,
$v=\frac{\omega }{k}=\frac{6\times 10^8}{4}=\frac{3}{2}\times 10^{8}m/s$
Refractive index, $\mu =\frac{c}{v}=\frac{3\times 10^8}{(3/2)\times 10^8}=2$