GCSE Physics: Radioactivity

Radioactivity carries some of the most reliably-asked questions in GCSE Physics: the properties table for the three radiation types, half-life data handling, and the contamination-versus-irradiation distinction appear year after year. This quiz drills all of them with concrete numbers.

The properties questions cover alpha, beta and gamma as the specification tabulates them: what each actually is (a helium nucleus, a fast electron from the nucleus, high-energy electromagnetic radiation), their penetrating power against paper, aluminium and lead, and the inverse relationship between ionising power and penetration that makes alpha the most ionising but least penetrating. A stopping-materials question applies the table practically.

The decay questions work the nuclear bookkeeping: in alpha decay the mass number falls by 4 and the atomic number by 2 (uranium-238 to a daughter of mass 234), while in beta decay a neutron becomes a proton, raising the atomic number by 1 with the mass number unchanged. Both directions — predicting the daughter and identifying what changed — are covered.

The half-life questions use realistic data: an 800 Bq source with a 2-hour half-life read forward through three halvings to 100 Bq, and the reverse skill of extracting a 5-minute half-life from a count rate falling from 120 to 15 in 15 minutes. The random, unpredictable nature of individual decays gets its own conceptual question, as does the contamination/irradiation distinction — radioactive material on or in an object versus exposure to radiation from outside — which the specification calls out explicitly and students routinely blur. Worked explanations show every halving chain and every mass-number ledger in full.

• Compare alpha, beta and gamma radiation by composition, penetration and ionising power
• Track mass number and atomic number changes through alpha and beta decay
• Calculate remaining activity after a given number of half-lives
• Determine a half-life from count-rate data
• Distinguish contamination from irradiation and explain the random nature of decay

Topic scope follows the Atomic structure section of the Department for Education's GCSE combined science and physics subject content: the properties of alpha, beta and gamma radiation, nuclear equations, half-life, the random nature of radioactive decay, and radioactive contamination versus irradiation.