Question

find the wavelength of radio waves of frequency 200kHz

Answer 1

$\lambda = \frac{c}{f}$
λ - wavelength, c - the speed of light, f - frequency

$f=200 \ kHz= 200 000 \ Hz \\ \\ \lambda=\frac{300 000 \ [\frac{km}{s}]}{200 000 \ [Hz]}=\frac{3}{2}=1.5 \ [km]$

The wavelength of these waves is 1.5 km.

Answer 2

For any wave, Wavelength = (speed) / (frequency)

For radio waves, Speed = about 3x10⁸ meters per sec ("speed of light")

So Wavelength = (3 x 10⁸ m/s) / (200 x 10³ /sec) = 1,500 meters