Fast electrons through air mostly have elastic scattering making their long distance path a 3D random walk with exponential dropoff which dominates the inverse square geometric dropoff.
Sr90 beta decays emitting an electron becoming daughter decay product Yttrium-90. Yttrium-90 then beta decays (after a half-life of a few days) emitting more energetic electrons than Sr90, and those electrons travel a mean distance through STP air of maybe meters and effectively don't travel further than say 10m.
At long distance through air the Bremsstrahlung xray radiation dominates? It is generated by the fast electrons curving when passing close to nuclei. Xrays through air are inverse square? I guess it depends on the absorbtion characteristics of air.
AFAIK the above is mostly correct but I haven't checked anything properly sorry.
Basically anything to do with radiation is usually deeply complex and you need to look at all the different factors before making assumptions.
Comments
Fast electrons through air mostly have elastic scattering making their long distance path a 3D random walk with exponential dropoff which dominates the inverse square geometric dropoff.
Sr90 beta decays emitting an electron becoming daughter decay product Yttrium-90. Yttrium-90 then beta decays (after a half-life of a few days) emitting more energetic electrons than Sr90, and those electrons travel a mean distance through STP air of maybe meters and effectively don't travel further than say 10m.
At long distance through air the Bremsstrahlung xray radiation dominates? It is generated by the fast electrons curving when passing close to nuclei. Xrays through air are inverse square? I guess it depends on the absorbtion characteristics of air.
AFAIK the above is mostly correct but I haven't checked anything properly sorry.
Basically anything to do with radiation is usually deeply complex and you need to look at all the different factors before making assumptions.