How gamma radiation is able to penetrate thick layers of material, whilst alpha and beta hardly penetrates skin?

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How gamma radiation is able to penetrate thick layers of material, whilst alpha and beta hardly penetrates skin?

In: Physics

It has to do with what this radiation actually is.

Alpha radiation is two protons and two neutrons (essentially an He nucleus without any electrons).

Beta radiation is an electron that is not attached to a nucleus.

Gamma radiation is a very high frequency electromagnetic wave (light that is beyond the visible spectrum).

Because Alpha and Beta particles have a net electric charge, they react strongly with the electrical forces of the atom in normal material, and thus stop within those materials rather than passing through largely unimpeded.

Because Gamma is just a form of light, it doesn’t have the electrical charge that Alpha and Beta do, and thus can pass through more stuff before it interacts with something that will stop it.

Another aspect is how it ionises (pulls electrons off) stuff (molecules, etc.)

For alpha particles, they have a high charge, so it ionises things the most easily.

For beta particles, they have a lower charge, so they ionise less easily than alpha particles.

These two only have to get close to other molecules (or atoms, or compounds) in order to ionise them, so they won’t travel very far before they’re “used up”*.

For gamma radiation, its just energy, so you can think about it as a photon, which has no charge. This means it has to physically hit an electron before it can ionise it, so the photons travel quite far before they’re “used up”*.

*obviously very simplified