Question

The velocity of $\alpha -rays$ is approximate:
(a)- Equal to the velocity of light
(b)- $\dfrac{1}{10}$th of the velocity of light
(c) 10 times more than the velocity of light
(d)- None of these

Answer 1

The alpha–rays are the rays which consist of alpha-particles having + 2 electronic charge. The velocity of the alpha-rays or $\alpha -rays$ is $2\text{ x 1}{{\text{0}}^{7}}\text{ m}{{\text{s}}^{-1}}$. The velocity of the light is denoted by c and its value is $3\text{ x 1}{{\text{0}}^{8}}\text{ m}{{\text{s}}^{-1}}$.

Complete Solution :
There are two protons and two neutrons in the alpha particle or $\alpha -particle$ which constitute the alpha- rays or alpha radiation. The electric charge of the alpha-particle is +2. In other words, we can say that the alpha-particle is a helium atom. These are produced by alpha-decay from heavy nuclei. The net spin of the alpha-particle is zero. The velocity of the alpha-rays or $\alpha -rays$ is $2\text{ x 1}{{\text{0}}^{7}}\text{ m}{{\text{s}}^{-1}}$.
- The velocity of the light is denoted by c and its value is $3\text{ x 1}{{\text{0}}^{8}}\text{ m}{{\text{s}}^{-1}}$.
So, from these two values, we can say that the velocity of the alpha-particle will be $\dfrac{1}{10}th$ velocity of the light.
- When a heavy nucleus is subjected to alpha-decay, high-speed radiations are bombarded on the nuclei due to which the emission of a large amount of energy takes place, and most of the energy gets converted into the kinetic energy of the alpha-particle.
So, the correct answer is “Option B”.

Note: We can represent the alpha- particle as $_{2}^{4}He$. When there is the removal of alpha-particles from the heavy nucleus, there is the formation of a nucleus having 4 unit atomic mass lesser and 2 unit atomic number lesser.