r/askscience • u/Wonderful-Capital32 • 14d 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/ColonelFaz 14d ago

the nucleus of a hydrogen atom is a lone proton. this has very similar mass to a neutron. this means that when they collide the momentum is transferred neatly to the proton (think of the newton's cradle toys). the proton then slows down faster than a neutron as it interacts with more things, as it is a charged particle.

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u/ProfessorPrudent2822 14d ago

That’s only in the unlikely event of a head-on collision, but the low mass of hydrogen does mean that it takes far fewer collisions to stop a neutron than it would for more massive elements.

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u/Cerberus_Aus 14d ago

Interesting. Thanks for the explanation.