Penetration

Alpha, beta and gamma radiation have different penetrating powers.

Alpha radiation has low penetrating power. It is stopped by: paper; outer layers of skin; * a short distance of air.

Beta radiation has medium penetrating power. It can pass through paper but is reduced significantly by suitable thin shielding materials.

Gamma radiation has high penetrating power. It requires much more substantial shielding to reduce its intensity effectively.

Alpha particles are charged and relatively massive, so they interact strongly with matter and lose energy quickly. Beta particles interact less strongly. Gamma photons are uncharged and can penetrate farther before interacting.

Alpha < Beta < Gamma