12 An X-ray beam is used to produce an image of a model of a thumb. A parallel beam of X-ray radiation of intensity I₀ is incident on the model, as illustrated in Fig. 12.1. [Figure 12.1] Data for the attenuation (absorption) coefficient μ in bone and in soft tissue are shown in Fig. 12.2. [Figure 12.2] (a) Calculate, in terms of the incident intensity I₀ of the X-ray beam, the intensity of the beam after passing through (i) a thickness of 2.8 cm of soft tissue, intensity = .............................................. I₀ (ii) the bone and soft tissue, as shown in Fig. 12.1. intensity = .............................................. I₀ (b) (i) State what is meant by the contrast of an X-ray image. (ii) By reference to your answers in (a), suggest whether the X-ray image of the model has good contrast.

1. (a)(i)a thickness of 2.8 cm of soft tissue, intensity = .............................................. I₀[2]
2. (a)(ii)the bone and soft tissue, as shown in Fig. 12.1. intensity = .............................................. I₀[2]
3. (b)(i)State what is meant by the contrast of an X-ray image.[2]
4. (b)(ii)By reference to your answers in (a), suggest whether the X-ray image of the model has good contrast.[1]

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