Type of Radiation | Alpha particle | Beta particle | Gamma ray |
Symbol | α | β | γ |
Mass (atomic mass units) | 4 | 1/2000 | 0 |
Charge | +2 | -1 | 0 |
Speed | slow | fast | very fast (speed of light) |
Ionising ability | high | medium | weak |
Penetrating power | low | medium | high |
Stopped by: | paper | aluminium | lead |
Alpha particle:
- It carries +2 charge and exerts greater forces on the neighbouring air molecules.
- It moves at a relatively low speed. The chance of ionising the neighbouring molecule is higher.
- It has a strong ionising power and it loses kinetic energy readily to ionise the air molecules along its path. So it has absorbed in the air quickly.
Beta particle:
- It carries -1 charge and exerts smaller forces on the air molecules.
- It travels faster and the chances of ionising the neighbouring molecules are lower.
- It has much weaker ionising power. So it loses kinetic energy at lower rate. Thus, it has a stronger penetrating power than alpha.
Gamma particle:
- It is electrically neutral and travels very fast at the speed of light.
- Ionising effects only occur when they collide directly with the air molecules. Since the chances for such a collision are very slim, gamma rays seldom produce ion pairs.
- It is a high frequency electromagnetic wave and it possess the highest energy.
- It has extremely weak ionising power. So it loses kinetic energy at the lowest rate.
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