Example

Radio 1 broadcasts on a frequency of 99.7 MHz.

Calculate the wavelength of Radio 1 waves.

Answer

Radio waves are electromagnetic waves and so their speed in a vacuum = 300,000,000 m/s.

v = f \lambda

v = 300,000,000 m/s

f = 99.7 MHz = 99.7 x 106 Hz

300,000,000 m/s = 99.7 x 106 Hz x \lambda

\lambda = \frac{\text{300,000,000}}{\text{99.7 x 10}^{6}}

\lambda = 3.0 m

The wavelength of Radio 1 waves is 3.0 m.

Question

State three differences between sound waves and electromagnetic waves.

  1. Sound waves are longitudinal, electromagnetic waves are transverse.
  2. Sound waves cannot travel through a vacuum, electromagnetic waves can travel through a vacuum.
  3. Sound waves travel at 330 m/s through air, electromagnetic waves travel much faster, at 300,000.000 m/s through air.