engineering
posted by julie on .
If a source is emitting particles at a rate of 15,000 particles per second, what is
the flux at 30 cm away from the source?

It depends upon the angular distribution of the emitted particles. If you are talking about radioactive decay, unless the nuclei are aligned (which is extremely unlikely) the emission will be isotropic, i.e, the same in all directionns.
The flux (emission per area) 30 cm away will then be
15,000 part/sec/(4*pi*R^2),
where R = 0.30 m 
isnt the area of a circle Pi*R^2?