Beta particles don't actually penetrate deeply into solids. They penetrate much less deeply than alpha particles, which are much heavier and less likely to be deflected by atomic interactions.

Here's why:

* Beta particles are electrons: They are much smaller and lighter than alpha particles (which are helium nuclei). This means they have less energy to penetrate matter.

* Interactions with atoms: Beta particles interact with the atoms in the solid through Coulomb interactions. These interactions can cause them to be deflected or lose energy, slowing them down.

* Range: The penetration depth of beta particles is called their range. The range depends on the energy of the beta particle and the density of the material it is passing through. Higher energy betas have a longer range.

Think of it this way:

Imagine throwing a pebble and a bowling ball at a wall. The bowling ball (alpha particle) is heavier and has more energy, so it will likely penetrate the wall further. The pebble (beta particle), on the other hand, will likely bounce off or get stopped quickly.

Here's a table summarizing the penetration depth of different particles:

| Particle | Penetration Depth |

|---|---|

| Alpha | Shortest |

| Beta | Medium |

| Gamma | Longest |

In conclusion: Beta particles are less penetrating than alpha particles because they are lighter and interact more frequently with matter. Their penetration depth is still greater than alpha particles, but they are much less likely to pass through thick materials like bone or metal.