Physics 9702 · AS & A Level · Production and use of ultrasound

Production and use of ultrasound — practice question

(a(i))[2]

Electrons in a vacuum are accelerated by a potential difference of $84\,\text{kV}$. They then collide with a metal target and X-rays are produced. Calculate the minimum wavelength of the X-rays that are produced.

(a(ii))[2]

The melting points of two metals are shown in Table 9.1. Suggest why the metal target is made from tungsten rather than copper.

(b)

As shown in Fig. 9.1, an X-ray beam is directed normally at a sample of soft tissue and bone. The data for the two materials are given in Table 9.2.

(c(i))[2]

Define the specific acoustic impedance of a medium in terms of its physical quantities.

(c(ii))[2]

Use data from Table 9.2 to calculate the percentage of the ultrasound intensity that is transmitted at a boundary between soft tissue and bone.

(c(iii))[2]

The ultrasound is now incident on the sample of soft tissue and bone shown in Fig. 9.1. Suggest two reasons why the transmitted intensity through the sample is less than the answer in (c)(ii).

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