The nuclius X undergoes α-decay and another nuclius Y, β– decay. Which of the following statements are correct ?
(i) The β–-particles emitted by Y may have widely different speeds.
(ii) The α -particles emitted by X may have widely different speeds.
(iii) The α-particles emitted by X will have almost same speed.
(iv) The β-particles emitted by Y will have the same speed.
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In nuclear decay, α-decay is a two-body process with discrete energy levels, so all α-particles from a specific decay have nearly the same kinetic energy (and thus speed). β⁻-decay is a three-body process (involving nucleus, electron, antineutrino), so the emitted β⁻-particles share energy with the antineutrino, resulting in a continuous spectrum of energies and widely different speeds.
Thus, for X (α-decay): particles have almost same speed. For Y (β⁻-decay): particles may have widely different speeds.
Therefore, statements (i) and (iii) are correct.