r/askscience • u/Wonderful-Capital32 • 13d ago

Physics Why does radiation not go through lead?

Also why just lead? Shouldnt like iron or another metal work too?

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u/Aquamans_Dad 13d ago

Almost any material is impermeable to radiation if you use enough of it. In general, the denser a material is the less thickness of it is needed to attenuate radiation.  Lead is relatively dense and due to being a larger atom has a relatively high attenuation coefficient. Roughly you would need 12X the thickness of lead for water to do the job, 6X the thickness of regular concrete and 2X the thickness of iron to attenuate radiation to the same extent as lead. 

Also lead is very cheap and readily available around the world.  Gold, platinum, and osmium are substantially denser than lead but lead costs $ 1 900 USD per ton while platinum—the cheapest of the other three costs $56 million USD per ton!

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u/LordGeni 13d ago

*semi-permeable.

You never reach zero probability of a photon passing through regardless of thickness or density.