An ultrasound pulse travels through a 20 mm layer of tissue P, then through 30 mm of tissue Q. It reflects at the far surface of Q and returns along the same path.
The speed is 1000 m/s in P and 1500 m/s in Q.
What is the total time between sending the pulse and receiving this echo?
80 μs80\ \mu\mathrm{s}80 μs
40 μs40\ \mu\mathrm{s}40 μs
100 μs100\ \mu\mathrm{s}100 μs
160 μs160\ \mu\mathrm{s}160 μs
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.