24.1 Production and use of ultrasound

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 changes.

Use —a piezo-electric crystal changes shape when a p.d. is applied across it and to connect the rule to the data and decision in the question.

This matters because —a piezo-electric crystal changes shape when a p.d. is applied across it and determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —a piezo-electric crystal changes shape when a p.d. is applied across it and to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —A piezo-electric crystal changes shape when a p.d. is applied across it and is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

understand how ultrasound waves are generated and detected by a piezoelectric transducer.

Use —ultrasound waves are generated and detected by a piezoelectric transducer to connect the rule to the data and decision in the question.

This matters because —ultrasound waves are generated and detected by a piezoelectric transducer determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —ultrasound waves are generated and detected by a piezoelectric transducer to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Ultrasound waves are generated and detected by a piezoelectric transducer is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

understand how the reflection of pulses of ultrasound at boundaries between tissues can be used to obtain diagnostic information about internal structures.

Use —the reflection of pulses of ultrasound at boundaries between tissues can be to connect the rule to the data and decision in the question.

This matters because —the reflection of pulses of ultrasound at boundaries between tissues can be determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the reflection of pulses of ultrasound at boundaries between tissues can be to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The reflection of pulses of ultrasound at boundaries between tissues can be is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

define the specific acoustic impedance of a medium as Z = ρc, where c is the speed of sound in the medium.

Use —the specific acoustic impedance of a medium as z = ρc to connect the rule to the data and decision in the question.

This matters because —the specific acoustic impedance of a medium as z = ρc determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the specific acoustic impedance of a medium as z = ρc to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The specific acoustic impedance of a medium as Z = ρc is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

use IR / I0 = (Z1 – Z2)2 / (Z1 + Z2)2 for the intensity reflection coefficient of a boundary between two media.

Use —ir / i0 = (z1 – z2)2 / (z1 + z2)2 for the intensity reflection coefficient to connect the rule to the data and decision in the question.

This matters because —ir / i0 = (z1 – z2)2 / (z1 + z2)2 for the intensity reflection coefficient determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —ir / i0 = (z1 – z2)2 / (z1 + z2)2 for the intensity reflection coefficient to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —IR / I0 = (Z1 – Z2)2 / (Z1 + Z2)2 for the intensity reflection coefficient is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

recall and use I = I0e–µx for the attenuation of ultrasound in matter.

Use —i = i0e–µx for the attenuation of ultrasound in matter to connect the rule to the data and decision in the question.

This matters because —i = i0e–µx for the attenuation of ultrasound in matter determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —i = i0e–µx for the attenuation of ultrasound in matter to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —I = I0e–µx for the attenuation of ultrasound in matter is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.