An Alpha (α) rapidly dissipates its energy as it ionise the medium due to its high mass and size. Therefore, its penetrating power is quite small. It can penetrate only through 3 to 8 cm in air. The penetrating power of γ-radiations is high. It is about 104 times that of α-particles and 102 times that of β-particles.
Order of penetration power : Alpha (α) < Beta (β) < Gamma rays (γ)