A plane electromagnetic wave travels in vacuum along z- direction. What can you say about directions

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8.Electromagnetic waves

easy

A plane electromagnetic wave travels in vacuum along $z-$ direction. What can you say about the directions of its electric and magnetic field vectors? If the frequency of the wave is $30 \;MHz$, what is its wavelength in $m$?

$10$

$25$

$15$

$2$

Solution

The electromagnetic wave travels in a vacuum along the $z$ -direction. The electric field $(E)$ and the magnetic field $(H)$ are in the $x-y$ plane. They are mutually perpendicular.

Frequency of the wave, $v=30 MHz =30 \times 10^{6} s ^{-1}$

Speed of light in a vacuum, $c=3 \times 10^{8} m / s$

$\lambda=\frac{c}{v}$

$=\frac{3 \times 10^{8}}{30 \times 10^{6}}=10 m$

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