Why are gamma rays much more penetrating compared with other types of radiation? Derive Eqn. 2 from Eqn. 1. Include a comment in the derivation as to why there is a negative sign in Eqn. 1. The mass absorption coefficient is defined as where is the density of the material. What does this property mean and why is it useful? Hint: Consider a situation where you have to design a system that absorbs a specific amount of gamma rays. What would you expect the linear coefficient of absorption values of Aluminium, Cop- per and Lead to compare to one another. Would you expect the same relation between the mass absorption coefficients?