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1. A radioactive sample has mass of 64g with a half-life of 3 days. On day 15, an additional 32g of the same isotope is added. What will be the total mass remaining after 24 days from the start?
2. A source produces alpha, beta, and gamma radiation. The radiation passes through a magnetic field going into the page. Which statement correctly describes the deflection?
3. Calculate the number of half-lives that have passed if a sample's activity drops from 256Bq to 6Bq. Give your answer to 1 decimal place.
4. Consider the decay equation: ²³⁸U → ²³⁴Th + X. After three more alpha decays and two beta decays, what is the mass number of the final isotope?
5. A Geiger counter records 400 counts/minute at 10cm from a source, and background radiation is 40 counts/minute. What is the true count rate at 40cm from the source in counts/second?
6. A radioactive source initially contains 3 different isotopes: A (half-life 1 day), B (half-life 2 days), and C (half-life 4 days). Initially they have equal activities. After 4 days, what is the ratio of their activities A:B:C?
7. If 5mm of lead reduces gamma radiation intensity to 25% of its original value, what thickness will reduce it to 1% assuming exponential decay?
8. A uranium-238 nucleus undergoes alpha decay followed by two beta decays. What is the change in atomic number from the parent to final nucleus?
9. A radioactive source is placed 1m from a detector. The count rate halves when a 2cm thickness of material X is placed between them. What thickness of material X would reduce the count rate to 3% of the original?
10. During β⁻ decay, an antineutrino is emitted along with the beta particle. Why is this necessary?