Answer: Beta particles cannot penetrate very far into solids because they have no mass.
Reason:
Penetrating power of particle depending upon the velocity and mass of particle. Greater the mass and velocity. Higher will be the penetrating power. In case of Beta particles, they are electrons. Mass of an electron is 9.1 X [tex] 10^{-31} [/tex] Kg. Due to such negligible mass, they have very low penetrating power.
