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i wanted to calculate the illumination at counter using inverse square law..(not a home work problem)

In my case i have a flat radioactive source (not point source) with a surface area of [tex]\pi(2.5)^2[/tex]mm[tex]^2[/tex]. Source ([tex]^{57}[/tex]Co) strength is [tex]1.85\times 10^9[/tex]Bq. Half-life=272 days. Now what will be the flux arriving at the detector placed 300 mm far from the source?

Second question: To convert Ci to Bq, we just multiply by [tex]3.7\times10^{10}[/tex]. Is there any other conversion to convert Ci to some 'X' by dividing by 9 ??

If some one knows some links/url/notes for calculating the count rate please reply me..

I dont how to apply the inverse [tex]^2[/tex] law!!!

Thanks for your reply.

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# Calculation of flux/

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