Why is alpha radiation dangerous inside the human body?
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Alpha particles are relatively large (two protons and two neutrons) and have a double positive charge (+2). Because of this, they interact strongly with other atoms. - **Ionisation:** They can easily knock electrons off atoms they pass, creating ions. This process is called ionisation. High levels of ionisation can damage or kill living cells, or cause mutations in DNA, which can lead to cancer. - **Penetration:** Because they interact so strongly, they lose their energy very quickly and cannot penetrate very far. They are stopped by skin or a few cm of air. - **Danger Inside the Body:** If an alpha-emitting source is ingested or inhaled, it is in close proximity to internal tissues. Its low penetration doesn't matter, but its high ionising power means it will cause intense, localised damage to the surrounding cells.