What you’ll learn6 learning objectivesChoose one objective for a focused lesson, or study the complete topic.24.1.1A piezo-electric crystal changes shape when a p.d. is applied across it and• understand that a piezo-electric crystal changes shape when a p.d. is applied across it and that the crystal generates an e.m.f. when its shape changesSyllabus objective24.1.2Ultrasound waves are generated and detected by a piezoelectric transducer• understand how ultrasound waves are generated and detected by a piezoelectric transducerSyllabus objective24.1.3The reflection of pulses of ultrasound at boundaries between tissues can be• understand how the reflection of pulses of ultrasound at boundaries between tissues can be used to obtain diagnostic information about internal structuresSyllabus objective24.1.4The specific acoustic impedance of a medium as Z = ρc• define the specific acoustic impedance of a medium as Z = ρc, where c is the speed of sound in the mediumSyllabus objective24.1.5IR / I0 = (Z1 – Z2)2 / (Z1 + Z2)2 for the intensity reflection coefficient• use IR / I0 = (Z1 – Z2)2 / (Z1 + Z2)2 for the intensity reflection coefficient of a boundary between two mediaSyllabus objective24.1.6I = I0e–µx for the attenuation of ultrasound in matter• recall and use I = I0e–µx for the attenuation of ultrasound in matterSyllabus objective