iGCSE Physics (0625) 5.2.3 Radioactive decay -Exam Style Questions Paper 1 - New Syllabus
▶️ Answer/Explanation
Detailed solution:
Beta-particles ($\beta^{-}$) are high-speed electrons emitted from the nucleus, not electromagnetic waves like gamma rays or X-rays.
They possess a relative charge of $-1$, making statement D correct, and they are highly ionising, making statement B correct.
During $\beta$-decay, a neutron changes into a proton ($n \to p + e^{-}$), which increases the proton number $Z$ by $1$.
Because the proton number defines the identity of an atom, the strontium-89 changes into a different element, making statement C correct.
Therefore, statement A is the only incorrect claim, as beta radiation consists of particles with mass and charge, not electromagnetic radiation.
▶️ Answer/Explanation
Detailed solution:
Radioactive decay involves the emission of radiation from an unstable nucleus to increase stability. In α-decay, the proton number decreases by 2. In β-decay, a neutron changes into a proton, increasing the proton number by 1. However, γ-radiation consists of high-energy electromagnetic waves rather than particles. Because it carries no charge and has no mass, the emission of a γ-ray does not change the proton number (Z) or the nucleon number (A) of the nucleus. Therefore, since the proton number remains unchanged, the event must be the emission of γ-radiation.
▶️ Answer/Explanation
Detailed solution:
Both alpha and beta decay involve a change in the number of protons in the nucleus, resulting in a different atomic number and thus a different element.
Gamma decay releases energy without changing the proton or nucleon number, so the element remains the same.
Therefore, both alpha-emission and beta-emission cause the nucleus to change into another element.
This corresponds to the image selection for Option A.