The three types of radioactivity in increasing order of penetrating power are?
alpha, beta, gamma
α-rays have the least penetrating power, they can penetrate a 0.01 mm thick Al foil.
β-rays have more penetrating power than alpha-rays, they can penetrate a 0.2 mm Al foil.
γ-rays have the highest penetrating power, they can penetrate a 1000 mm thick Al sheet.