A protective polymer lining is bonded to the inside of a storage vessel. A pulse-echo device sends ultrasound into the lining and receives echoes from its front and back surfaces.
The ultrasound has a frequency of 4.0 MHz and a wavelength of 0.60 mm in the polymer. The echoes arrive 18 μs18\ \mu\text{s}18 μs apart.
Calculate the thickness of the polymer lining.
112 exam-style questions on Edexcel GCSE Physics 4.3 Sound, ultrasound and infrasound, covering 4.3.1 Sound waves, vibrations and the human ear, 4.3.2 Ultrasound and infrasound, 4.3.3 Uses of ultrasound and infrasound, and 4.3.4 Sound waves passing between media. Each one has a worked solution and a mark scheme showing where the marks go.