An X-ray beam of initial intensity 50 Wm−2 is incident on soft tissue of attenuation coefficient 1.2 cm−1. Calculate its intensity after it has passed through a 5.0cm thickness of tissue.
A hint for this question is:
The attenuation coefficient is given in cm-1, hence you can leave the thickness in cm.
So according the hint I get the answer:
I=Ioe^(-ux)
50 x e^(-1.2x5)=
0.12Wm-2, which is the correct answer according to the textbook.
But why should I leave the attenuation coefficient and the thickness in cm, when the intensity is measured in W
m-2? I thought that the calculation should have been:
50 x e^(-0.0125x0.05)=
49.97Wm-2Confused, please help