Electronic watches keep accurate time using crystal oscillators. Inside the watch, there is a tiny block of quartz which vibrates. Two opposite faces of the block move alternately
toward each other and away from each other. This is caused by a standing wave in the block. The two opposite faces are at antinodes, and the plane halfway between these two
faces is at a node. If the two faces are 5.74 mm apart and the speed of sound in quartz is 3.72 km/s, find the frequency (kHz) of the vibration
Answer Range:200, 400 kHz