Question

Suppose that the electric field amplitude of electromagnetic wave is $E _{0}=120\, NC ^{-1}$ and its frequency if $f =50 \,MHz$. Then which of the following value incorrectly computed ?

• A. Magnetic field amplitude is $400 \,nT$.
• B. Angular frequency of EM wave is $\pi \times 10^{8} rad / s$
• C. Propagation constant (angular wave number) is $2.1\, rad / m$
• D. Wavelength of EM wave is $6\, m$.

Answer 1

Answer: (C)

$c =\frac{ E _{0}}{ B _{0}}$
$B _{0}=\frac{ E _{0}}{ c }$
$=\frac{120}{3 \times 10^{8}}=400\, nT$
$k =\frac{2 \pi}{\lambda}=\frac{2 \times 3.14}{6}$
$k \neq 2.1 \,rad \,m ^{-1}$