- #1

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could I request that the moderators move it to the right one.

Ok, so my problem is pretty much as I stated in the title.

The background to this is that I have been asked to roughly calculate the

number of alpha particles that would be incident on a detector surface

in an environment where there is 147 Bq m

^{-3}of alpha

particles from decaying Rn

^{222}.

So, I have taken the maximum range in air for an α-particle to be

3.4cm, so I am considering the decays in a hemisphere around the

detector which for simplicity's sake I am assuming to be a square of

side 1cm, and only has radiation incident on one side.

I have worked out the total activity in the hemisphere to be 1.22x10

^{-2}Bq, but I'm not sure how to proceed to work out how many

actually hit the sensor.

I believe it will probably involve some kind of volume integral, but

I'm not sure what to integrate!

I'm guessing that I plug something into the following equation

[itex]\int_0^π[/itex][itex]\int_0^π[/itex][itex]\int_0^R[/itex] r

^{2}sinθ dr dθ d[itex]\phi[/itex]

(I am also assuming the radiation to be isotropic)

If anyone could point me in the right direction it would be greatly

appreciated.

Many thanks