A detector receives echoes from the front and back surfaces of a metal plate. The second echo arrives 12 μs12\ \mu\mathrm{s}12 μs after the first. Sound travels at 5000 m/s in the plate. What is the plate thickness?
30 mm30\ \mathrm{mm}30 mm
120 mm120\ \mathrm{mm}120 mm
60 mm60\ \mathrm{mm}60 mm
15 mm15\ \mathrm{mm}15 mm
112 exam-style questions on Edexcel GCSE Physics 4.1 Wave properties, covering 4.1.1 Waves transfer energy and information, 4.1.2 Frequency, wavelength, amplitude, period and wavefronts, 4.1.3 Longitudinal and transverse waves, 4.1.4 The wave speed equations, 4.1.5 Measuring wave velocity, and 4.1.6 Calculating depth or distance from waves. Each one has a worked solution and a mark scheme showing where the marks go.