Sec 4 Combined Science (Physics) Radioactivity topical questions

Name the three types of particle in an atom and state the charge of each.

State what isotopes are.

Rank alpha, beta and gamma radiation from most to least penetrating, and state what stops each.

Define the half-life of a radioactive isotope.

For carbon-14 (¹⁴₆C): (a) state the numbers of protons, neutrons and electrons in a neutral atom; (b) explain why ¹²₆C and ¹⁴₆C are isotopes.

A source’s corrected count rate reads 640, 320, 160, 80 counts/min at 0, 10, 20, 30 minutes. (a) Determine the half-life. (b) Predict the corrected count rate at 40 minutes.

Compare alpha, beta and gamma radiation in terms of nature and ionising effect.

State what background radiation is, name two of its sources, and explain why source readings must be corrected for it.

For uranium-238 (²³⁸₉₂U): (a) state the numbers of protons, neutrons and electrons in a neutral atom; (b) uranium-235 is another isotope. State and explain how its nucleus differs; (c) write the nucleon and proton numbers of carbon-12 and state its neutron count.

A source has an initial corrected activity of 320 counts/min and a half-life of 8.0 hours. Calculate the corrected activity after (a) 8.0 hours, (b) 24 hours, (c) 32 hours.

A decay curve for a corrected count rate starts at 1000 counts/min and falls to 500 counts/min in 3.0 minutes. (a) Determine the half-life. (b) State the count rate at 9.0 minutes. (c) Estimate the count rate at 15 minutes. (d) Explain why actual readings fluctuate around these values.

Radioactivity is used in medicine and industry. (a) Explain why gamma radiation is suitable for sterilising sealed syringes. (b) Explain why a beta emitter suits a paper-thickness gauge. (c) State two hazards of handling radioactive sources and two precautions.