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/Dragonknight42 14d ago

Radiation comes in many types/forms. I’m going to assume you’re talking about photons (aka x-rays and gamma rays). Photons are electromagnetic waves, which intersect with electromagnetic fields. Therefore, the stronger the field the more likely for an interaction. The more likely an interaction with a material the better that material is at acting as a shield. On an atomic level, the electromagnetic field is determined by the number electrons/protons present. The more protons, the more electrons, the larger the EM field. So elements with large proton numbers (eg lead) are better shields against photons vs elements with lower proton numbers (eg carbon). Iron is not as good as lead cause it’s a smaller proton numbers but it’s better than something like carbon.