In traversing a distance `d` the fraction which is either scattered or absorbed is clearly
`1-e^(-n(sigma_(s)+sigma_(a))d)`
by the usual definition of the attenuation factor. Of this, the fraction scattered is (by defination of scattering and absorption cross section)
`w={1-e^(-n(sigma_(s)+sigma_(a))d)} (sigma_(s))/(sigma_(s)+sigma_(a))`
In iron `n=(rhoxxN_(A))/(M)=8.3xx10^(22)per c c`
Substitution gives `w=0.352`