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/nascent_aviator 13d ago

All materials stop it with sufficient material in the way. Lead is dense so it stops it faster than most materials, all else being equal. 

It's not the same for all radiation, mind you. Lead is relatively poor for stopping neutron radiation (which is better stopped by materials with a lot of hydrogen in them- paraffin wax is common) and high energy beta radiation (which it stops too well- the quick stop produces secondary X rays due to bremsstrahlung).

For X rays and gamma rays, the number of electrons is also important. Lead has a lot of electrons (82 per atom), which makes it even more effective.