How is a piezoelectric crystal used to generate waves of ultrasound?
A piezoelectric crystal makes use of the peizoelectric effect. This is the production of a voltage when mechanical stress is applied across the material. This occurs only in materials when the unit cells which make up the material have an asymmetric charge distribution when under compression.
The reverse of this is using the crystal to produce waves. This is the reverse peizoelectric effect. This means appying a voltage to the crystal, producing compression. When an alternating current is applied, this gives repeated compression and relaxation of the crystal.
The movement of the face of the crystal will displace air molecules, giving a longitudinal wave, meaning, at the necessary high frequency, ultrasound waves.
DA
Related Physics A Level answers
All answers ▸Define electrical resistance
On the line of centres between the Earth and the Moon, there is a point where the net gravitational force is zero. Given that the distance between the two is 385,000 km, and that the Earth has a mass 81x that of the Moon, how far is this point from Earth?
There is a point between the Moon and the Earth where the gravitational attractions are equal and opposite. How much further is this point from the Earth than the Moon
What is the mathematical relationship between the frequencies of musical notes that we perceive identical, but at different octaves?