A level: Ultrasound Questions
Q6.The diagram shows a cross-section through an ultrasound generator.
![](graphic4.png)
(a) Explain the purpose of the backing material.
It damps the oscillation of the crystal to zero quickly
when the driving signal is removed ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(2 marks)
(b) State the main difference between the probe used in an A-scan and that used in a B-scan.
An A-scan has a single transducer, but a B-scan uses a multi-transducer probe ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(1 mark)
(c) The diagram belowshows the display on an oscilloscope screen of an A-scan to find the size of an organ. The speed of sound in the organ is 1200 m s-1
![](graphic1ANS2.png)
(i) Calculate the diameter of the organ.
Time for pulse to go the double distance
= 0.27 0.12 = 0.15 ms ![](../../../../graphics/symbols/nuclides/ticksmall.png)
diameter = (1200 × 0.15 × 10-3)/2 = 0.090 m ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(ii) State two processes which reduce the strength of the reflected signal received by the probe.
You only get a partial reflection at boundary
You also get attenuation as the signal passes through body ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(4 marks)
(Total 7 marks)