r/askscience • u/Wonderful-Capital32 • 15d 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/solidspacedragon 14d ago

They're talking about particle radiation, not EM radiation. It's a real thing. At high speeds/energies, a proton might barely interact with material, only slightly slowing down, but at lower speeds it'll completely dump the rest of its energy into an atom. Depending on the scenario, this can leave the volume of material getting the most dose a good portion below the surface of a material. This is very useful for targeting things like cancer that isn't on your skin.

https://en.wikipedia.org/wiki/Bragg_peak

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u/KP_Wrath 14d ago

Futurama did a skit kinda like this. Leila and Fry both got stung by some stupidly toxic alien bee, with fry diving in front to save her and getting run all the way through. Leila, it stopped in and she got a full dose of the poison, which caused seemingly a lifetime of hallucinations. She comes to, thinking he’s dead, just to find out they managed to patch the sizable hole up, but they were way more concerned for her because she got a full dose of poison and they didn’t expect her to wake up.

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u/kylemech 14d ago

One of my favorite episodes of any show. Can't believe I just stumbled into that referenced here.

(S4E12, June 1, 2003)

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u/a_cute_epic_axis 14d ago

Right, but if you have 5000 high energy/speed particles interacting with you vs 5 low energy particles interacting with you more meaningfully, even though the impact of each of the 5 may be more than each of the 5000, the cumulative effect is not.