Gamma radiation sorce sheilding

[taylor.simon]

Homework Statement

a gamma raidiation source (226Ra) is used in 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 without shielding? assume the shield material is a) concrete B)lead C) steel note the half thicknesses are 0.12m, 0.014m ,0.018m respectively

part 2
as an alternative to shielding of the radiation source in the above question is to extend the distance between the radiation and the worker if the initial design placed the worker at 1m and then the design was review and place the source 10m what percentage reduction in radiation exposure would there for the second position relative to the first

Homework Equations

part 1 n=-2/log1/2
part 1 df/di = (ri/rf)^2 ri=1m rf=10m

The Attempt at a Solution

i have no idea how to do ether i asked the lecturer and he said there was a way without have to do logarithms for the first part but didn't explain how and i need to know how for my exams please and help is greatly appreciated!

 

[Rajini]

Hi,
Part 1:
Please use Lambert's law.
<br /> \frac{I_{\rm mat}}{I_0}=\exp[\frac{-\mu}{\rho}t_{\rm mat}\rho].<br />
Where 'mat' represent the material used for shielding (concrete or lead or steel)
I_mat is the amount that you get after shielding
I₀ is just the source strength or amount without shielding
\rho is density
t_mat is thickness of the material
\mu is linear attenuation coefficient.
Part 2:
I don't understand. But maybe you need to use inverse square law.
hope it helps.