A speaker emits a sound wave through a metallic block, with a speed of 0.42 km/s, and a frequency of 16kHz. Calculate the wavelength to 3.s.f. Describe the characteristics of a longitudinal wave.

Firstly the values should be converted into more comfortable units. 0.42km/s = 420m/s, and 16kHz = 16,000Hz. Next, use the equation wavelength = speed/frequency This gives wavelength = 420m/s over 16,000/s = 0.02625, which gives 0.0263m, to 3.s.f. In longitudinal waves, particles propagate (travel) in the same direction as the wave. Longitudinal waves create areas of high and low density, called compressions and rarefactions respectively.