Q. Among Alpha, Beta and Gamma radiations:
- The Alpha Particles have highest ionising power but least penetrating power
- The Gamma radiations have highest penetration power but lowest ionising power
Which among the above is / are correct statements?
Answer:
Both 1 & 2
Notes: Alpha particles:
- They are doubly ionized helium nuclei having a mass equal to 6.64 × 10–27 kg and charge equal to 3.2 × l0–19 C.
- They have the highest ionizing power.
- They have the least penetrating power.
- They produce fluorescence in the zinc sulphide screen.
Beta particles:
- They are negatively charged particles, having a charge equal to –1.6 × 10–19 C and mass 9.1 × 10–31 kg.
- They have more penetration power than alpha particles.
- They have more ionizing power than alpha particles.
- They affect photographic plate.
Gamma radiations:
- They are electromagnetic waves, having wavelength less than 0.01 Å.
- They have a very high penetration power.
- They have a very low ionizing power.
- They are not affected by electric or magnetic fields.
Notes on Ionizing power: If one unit is ionizing power of alpha radiations, then 100 units is ionizing power of beta particles and 10000 units is the ionizing power of gamma particles.
Notes on Penetration power: Gamma radiations can penetrate even 30 cm of iron. Alpha particles can penetrate 1mm of lead or 5 mm of aluminium. Alpha particles can penetrate 2.7 to 8.6 cm of air.