Question

The least penetrating radiation is :

• A. γ-radiations
  
• B. β-particles
  
• C. X-rays
• D. α-particles

Answer 1

The correct option is D α-particles

The penetrating power of γ-radiations is highest. It is about ${10}^4$ times that of α-particles and ${10}^2$ times that of β-particles.
An α-particle rapidly loses its energy due to its high mass and huge size, as it moves through a medium. It interacts most with the surrounding medium and hence loses energy and therefore its penetrating power is low.
Correct answer: (a) α-particles