A gamma radiation source (226Ra) is used in a hospital laboratory. If shielding is considered as a means of control, how many centimeters are needed to reduce the radiation to 1% of what a worker would be exposed to with out shielding? Assume the shielding material is (a) concrete, (b) steel and (c) lead. (Note: You will need to us the half-thicknesses of each material)
Concrete: Half thickness = 0.12m
Steel: Half thickness = 0.018m
Lead: Half thickness = 0.014m