A-LevelPhysicsMedical physics9702/41 · May/June 2017 · Q105 Marks

State what is meant by the hardness of an X-ray beam,

(a)(i)State what is meant by the hardness of an X-ray beam,[2]
(a)(ii)how the hardness of an X-ray beam from an X-ray tube is increased.[1]
(b)The same parallel beam of X-ray radiation is incident, separately, on samples of bone and of muscle. Data for the thickness x of the samples of bone and of muscle, together with the linear attenuation (absorption) coefficients μ of the radiation in bone and in muscle, are given in Fig. 10.1. [Figure 10.1] Determine the ratio intensity transmitted through bone intensity transmitted through muscle[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.

[M1] penetration of beam
[A1] greater hardness means greater penetration/shorter wavelength/higher frequency/higher photon energy
[B1] greater accelerating potential difference
[B1] or greater p.d. between anode and cathode
[C1] I = I₀ exp(−μx)
[C1] ratio = (exp {−1.5 × 2.9}) / (exp {−4.0 × 0.95}) (= exp {−0.55})
[A1] = 0.58

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