12. a) Sound waves travel at a speed of 340 m s¹ in air
at 20°C. If the frequency of these waves is 2.5 kHz,
what is their wavelength?
b) Infra-red electromagnetic waves travel at a
speed of 3.0 x 108 m s¹. Calculate the frequency of
these waves if their wavelength is 1.2 x 10-6 m.