Edexcel GCSE Physics: Radioactivity

There are three main types of nuclear radiation: alpha (α), beta (β) and gamma (γ).

Describe and explain the differences between alpha, beta and gamma radiation. In your answer you should refer to the nature (what each one is), the charge, the penetrating power (what stops each), and the ionising power of each type. (6 marks)

A sample of a radioactive isotope is monitored with a detector. The count rate (corrected for background radiation) is recorded over time.

Time / hours	Count rate / counts per minute
0	800
3	400
6	200
9	100
12	50

(a) Use the data to determine the half-life of the isotope. Explain how you obtained your answer. (3 marks)

(b) Predict the count rate after a further 3 hours (i.e. at 15 hours). (1 mark)

A radioactive isotope has a half-life of 5 years. A sealed source initially contains 2.4 × 10¹² undecayed nuclei.

(a) Calculate the number of undecayed nuclei remaining after 15 years. Show your working. (2 marks)

(b) State what is meant by the half-life of a radioactive isotope. (1 mark)

When working with radioactive materials, scientists distinguish between irradiation and contamination.

(a) Explain the difference between being irradiated by a radioactive source and being contaminated by one. (2 marks)

(b) Name one source of the background radiation that is always present around us. (1 mark)

Inside the Sun, hydrogen nuclei join together to release energy in a process called nuclear fusion.

Explain what is meant by nuclear fusion, and state why very high temperatures are needed for it to occur. (2 marks)

Atoms of the same element can exist as different isotopes.

State what is meant by two atoms being isotopes of the same element. (1 mark)