SMS(S) Radioactivity WS 1 Qn

1 S St. Margaret’s School (Secondary) Department of Science Physics Name: …………………………………………… Class: …………. Date: …………. 1 Which type of radiation consists of electrons? A alpha-particles B beta particles C gamma-rays D X-rays 2 A sample of a radioactive isotope produces a count rate of 10 000 counts per minute. The half-life of the isotope is one day. What was the count rate of the sample two days ago? A 2500 counts per minute B 5000 counts per minute C 20 000 counts per minute D 40 000 counts per minute 3 Which nucleus is produced when americium-241 ( 𝐴𝐴𝐴𝐴95 241 ) emits an alpha-particle? A 𝑁𝑁𝑁𝑁93 237 B 𝐵𝐵𝐵𝐵97 237 C 𝑁𝑁𝑁𝑁93 245 D 𝐵𝐵𝐵𝐵97 245 4 Which states the three types of radiation emitted by radioactive isotopes in order of their ionizing effect from highest to lowest? A alpha-particles, beta-particles, gamma-rays B alpha-particles, gamma-rays, beta-particles C beta-particles, gamma-rays, alpha-particles D gamma-rays, beta-particles, alpha-particles

2 5 Which statement about the half-life of a radioactive isotope is correct? A Half-life changes as the isotope decays. B Half-life is the time it takes for the nucleon number of the isotope to halve. C Half-life is half the time it takes for the number of nuclei of the isotope to decrease to zero. D Half-life is the time it takes for the number of nuclei of the isotope to decrease by half. 6 A factory continuously produces plastic sheets. A radioactive isotope and a detector are used to check the thickness of the sheets. What is the most suitable source to use? A an alpha source with a half-life of a few minutes B an alpha source with a half-life of several years C a beta source with a half-life of a few minutes D a beta source with a half-life of several years 7 A source contains a radioactive material. Without the radioactive source present, a detector records a background count rate of 20 counts per minute. This source is placed in a fixed position near the detector. Initially a count rate of 520 per minute is recorded. Which count rate is recorded after a time of two half-lifes of the radioactive source? A 125 counts per minute B 130 counts per minute C 135 counts per minute D 145 counts per minute

3 8 A nucleus of 𝑃𝑃𝑃𝑃84 215 decays by emitting an alpha-particle and the resulting nucleus then decays by emitting a beta-particle. What is the nucleon number and proton number of the final nucleus? Nucleon number Proton number A 211 81 B 211 83 C 212 81 D 212 83 9 The half-life of a radioactive isotope is 24 hours. A sample of this isotope produces an initial count rate of 720 counts per second. How long does it take for the count rate to fall to 90 counts per second? A 3 hours B 72 hours C 96 hours D 192 hours 10 Which type of electromagnetic radiation is produced during radioactive decay? A alpha-particles B beta-particles C gamma-rays D X-rays 11