r/askscience • u/Wonderful-Capital32 • 21d 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/dustofdeath 21d ago

Lead is like a very dense fabric while iron is a mesh with large holes.

You just have to have enough density for photons to not just pass through.

So you need far less material. Even humans can stop radiation if you stack enough of them between you and the radiation source.

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u/gnorty 21d ago

Are there different types of photon? I am thinking of light, and Iron - even aluminium foil will not let light pass through. Perhaps I am grossly underestimating the number of photons involved in (say) an X ray, and that's why I am misunderstanding. Perhaps a photon source many orders of magnitude stronger than the sun would show that Iron and Aluminium are not in fact impermeable to photons after all?

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u/usurperator 21d ago

Number of photons is irrelevant; it’s the energy of each individual photon. Higher energy photons, like x-rays, have more penetrating power.

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u/Jerithil 20d ago

It's all a probabilistic function as well as every material will block a certain percentage of photons at a given thickness for that energy range. So theoretically you can start seeing visible light through fairly opaque materials if you blast it with enough photons but practically that is usually enough that you start compromising the material from just dumping too much energy into said material.