A factory uses an ultrasound sensor to monitor a rubber conveyor belt. The sensor sends a pulse into the belt and detects echoes from its near and far surfaces. The belt is 12 mm thick, and ultrasound travels through it at 1500 m/s.
What is the time difference between the two echoes?
32 μs32\ \mu\mathrm{s}32 μs
1.6 μs1.6\ \mu\mathrm{s}1.6 μs
16 μs16\ \mu\mathrm{s}16 μs
8.0 μs8.0\ \mu\mathrm{s}8.0 μs