Question

Consider $\alpha -particles,\beta -particles$, and $\gamma -rays$, each having an energy of 0.5 MeV. In increasing order of penetrating powers, the radiations are

• A. $\alpha ,\beta ,\gamma$
• B. $\alpha ,\gamma ,\beta$
• C. $\beta ,\gamma ,\alpha$
• D. $\gamma ,\beta ,\alpha$

Answer 1

Answer: (A)

$\alpha ,\beta ,\gamma$

The bigger the particle, the more likely it is to have a collision with the atoms of the material.The collision will stop the particle going through the material.
alpha particles are the biggest, beta particles are very much smaller and gamma rays have no mass.
Alpha particles are the biggest and are least able to penetrate a material. Paper or smoke particles will stop them.Even in air, alpha particles can only travel for a few centimetres before they are stopped by collisions with the air molecules.
Beta particles are stopped by a few millimetres of aluminium but some beta particles will penetrate thin aluminium foil or paper.
Gamma rays are the most able to penetrate and will even find their way through metres of concrete.The ability of radioactivity to pass through materials is called its penetrating ability. Penetrating ability depends on the size of the radioactive particle.