How the Radiations Behave
How the Radiations Behave
- The three radiations differ in how strongly they ionise matter, how far they travel, and how fields bend them.
Ionising power and penetration
- As radiation passes through matter it knocks electrons off atoms. This is called , and it is how the radiation loses its energy.
- Alpha is the most ionising: it is slow and highly charged, so it interacts strongly and loses its energy quickly. Because it loses energy quickly, it does not travel far. Paper or a few centimetres of air stops it. Most ionising, least penetrating.
- Gamma is the least ionising: with no charge it barely interacts, so it hardly loses energy and travels a long way. Thick lead only reduces it; it is never fully stopped. Least ionising, most penetrating.
- Beta is between the two, stopped by a few millimetres of aluminium. The pattern is: the more strongly a radiation ionises, the less far it travels, because it loses its energy sooner.
| Alpha (α) | Beta (β) | Gamma (γ) | |
|---|---|---|---|
| ionising power | strong | medium | weak |
| penetration | low | medium | high |
| stopped by | paper / few cm air | few mm aluminium | thick lead (only reduced) |
Common mistake
It looks odd that alpha is the most ionising yet the least penetrating. The two go together: alpha ionises so strongly because it interacts with everything in its path, and that is exactly why it loses its energy and stops so soon.
Bending in electric and magnetic fields
- Fields bend charged radiation, so they separate the three by charge.
- Alpha () and beta () bend in opposite directions, because their charges are opposite. Gamma (no charge) goes straight through.
- Beta bends much more than alpha. Even though alpha has more charge, it is thousands of times heavier, and heavy particles are hard to deflect.