Question

Which radiation has maximum ionization power?

• A. Alpha
• B. Beta
• C. Neutron
• D. Gamma

Hint:

Ionizing power rises with charge and falls with speed; the slow, doubly charged particle wins.

Answer 1

The Correct Option is A

Step 1: Ionizing power measures how many ion pairs a radiation creates per unit path length as it moves through matter. It grows with the particle's charge and with how slowly it moves, because a slow, highly charged particle spends more time interacting with atomic electrons.

Step 2: Compare the four radiations. An alpha particle is a helium nucleus with charge \(+2e\) and a large mass, so it moves slowly and interacts very strongly. A beta particle carries charge \(-e\) and is light and fast, so it ionizes less. A gamma ray is an uncharged photon and ionizes only weakly and indirectly. A neutron is uncharged and interacts through nuclear collisions, so its direct ionization is very small.

Step 3: Because the alpha particle has the highest charge and the lowest speed, it produces the densest trail of ion pairs. Roughly, \[\text{ionizing power:}\quad \alpha \gg \beta \gg \gamma.\]

Step 4: The maximum ionizing power belongs to alpha radiation, so option (A) is correct. (Note that alpha also has the least penetrating power, which is the opposite ordering.)

\[\boxed{\text{Alpha}}\]