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
This must be converted to Hz to use in the wave speed equation.
99.7 MHz = 99.7 x 106 Hz
300,000,000 = 99.7 x 106 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.
- Sound waves are longitudinal waveA wave that moves in the same direction as the direction in which the particles are vibrating., electromagnetic waves are transverseAt 90 degrees. In transverse waves, the vibrations are at 90 degrees to the direction in which the waves travel..
- Sound waves cannot travel through a vacuumA volume that contains no matter., electromagnetic waves can travel through a vacuum.
- Sound waves travel at 340 m/s through air, electromagnetic waves travel much faster, at 300,000.000 m/s through air.