X-rays are incident on an aluminium sheet of thickness 8.0 cm. Calculate the fraction of the incident X-ray intensity that emerges from this sheet for photon energies of

(i) 9.0 MeV.

(ii) 3.0×10⁻³ MeV.

With reference to your answers to (a)(i) and (a)(ii), discuss the advantages of using the aluminium sheet.

(i) $\mu  = 2.7 \times {10^{ - 3}}\left( { \pm 0.3 \times {{10}^{ - 3}}} \right)$
So $\frac{I}{{{I_{\rm{O}}}}} =  \ll {e^{ - \mu x}} = {e^{ - \left( {2.7 \times {{10}^{ - 3}} \times 8 \times {{10}^{ - 2}}} \right)}} \gg  = 0.9999 \approx 1.0$

(ii) $\ll \mu  = 50{\rm{to give}} \gg \frac{I}{{{I_{\rm{O}}}}} = 1.8 \times {10^{ - 2}}$

low energy radiation removed but not high energy radiation

radiation has narrower range of energies

only necessary radiation reaches the patient making it safer