A vial contains a sample of a radioactive solution. The half-life of the radioactive substance is known to be 15 hours15\text{ hours}15 hours. It decays by β\betaβ-particle emission.
A radiation detector, held close to the solution, records a count rate of 1200 counts/min1200\text{ counts/min}1200 counts/min, after subtraction of the background count rate.
A time of 15 hours15\text{ hours}15 hours is allowed to elapse after recording the 1200 counts/min1200\text{ counts/min}1200 counts/min count rate. A new count rate is then taken.
Calculate the new count rate due to the radioactive solution.
How many radioactive atoms of the original type remain in the sample after the 15 hours15\text{ hours}15 hours have elapsed? Choose one option:
How many atoms in total remain in the sample after 15 hours15\text{ hours}15 hours has elapsed? Choose one option:
The sample contains sodium-24 (1124Na^{24}_{11}\text{Na}1124Na).
For one atom of 1124Na^{24}_{11}\text{Na}1124Na, state:
its nucleon number,
its proton number,
its number of neutrons.
484 exam-style questions on CIE IGCSE Physics 5.2 Radioactivity, covering 5.2.1 Background radiation and measuring count rate, 5.2.2a Alpha, beta and gamma emission, 5.2.2b Deflection and ionising effects of nuclear radiation, 5.2.3a Radioactive decay, 5.2.3b Effects of decay on the nucleus and decay equations, 5.2.4a Half-life, 5.2.4b Choosing isotopes for applications, and 5.2.5 Effects of ionising radiation and safety precautions. Each one has a worked solution and a mark scheme showing where the marks go.