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 In the Geiger-Marsden experiment, a beam of apha-particles is fired at a very thin sheet of gold foil, in a vacuum. What is deduced from this experiment? A Alpha-particles are repelled by electrons. B Atoms contain air. C Electrons are found in atomic nuclei. D Nuclei are much smaller than atoms.

4 12 A radioactive isotope 𝐶𝐶⬚ 14 emits beta-particles. A sample of this isotope is left for a period of time that is equal to its half-life. Which two quantities decrease to half of their initial value during this time? A the decay rate and the number of protons B the mass of the sample and the number of 𝐶𝐶⬚ 14 nuclei C the number of 𝐶𝐶⬚ 14 nuclei and the decay rate D the number of protons and the mass of the sample 13 Which row gives the range and electrical charge of an alpha-particle? range in air electrical charge A a few centimetres negative B a few centimetres positive C a few metres negative D a few metres positive 14 Which row states the nature and range of beta-particles in air? nature range in air A electromagnetic radiation 1 – 10 cm B electromagnetic radiation 10 – 100 cm C electron 1 – 10 cm D electron 10 – 100 cm

5 15 Three types of radiation emitted by unstable nuclei are electrons, helium nuclei and electromagnetic radiation. What are these types of radiation? electrons helium nuclei electromagnetic radiation A alpha beta gamma B alpha gamma beta C beta alpha gamma D beta gamma alpha 16 A sample of wood contains 9.0  1016 nuclei of carbon-14. The nuclei undergo radioactive decay with a half-life of 5600 years. How many carbon-14 nuclei remain in this sample after 16 800 years? A 1.1  102 B 1.1  1016 C 3.0  1016 D 4.5  1016 17 People working with radioactive materials use a photographic film badge covered in paper. The badge is used to monitor the level of their exposure to radiation. Which radiation is detected? A alpha-particles only B beta-particles only C gamma-rays and beta-particles D gamma-rays only 18 When a radioactive atom decays by alpha-particle emission, its nucleus loses A 1 proton only. B 1 proton and 1 electron. C 2 protons and 2 electrons. D 2 protons and 2 neutrons.

6 19 A school keeps radioactive sources for use in radioactivity experiments in a laboratory. The background radiation is measured at the start of an experiment. Which statement is correct? A The background radiation is caused by the school’s radioactive sources in the laboratory. B The background radiation is present when there are no radioactive sources in the laboratory. C The background radiation is radiation that is not detected in radioactivity experiments. D The background radiation is the same in laboratories in different countries. 20 The count rate from a radioactive source falls from 4000 counts per minute to 500 counts per minute in 72 minutes. What is the half-life of the source? A 8 minutes B 9 minutes C 18 minutes D 24 minutes 21 What are the characteristics of an alpha-particle? charge ionizing effect A negative strong B negative weak C positive strong D positive weak

7 22 Alpha-particles pass through an electric field or a magnetic field. How is the path of the particles affected by these fields? electric field magnetic field A deflected deflected B deflected undeflected C undeflected deflected D undeflected undeflected 23 Which row is correct for nuclear fission and for nuclear fusion? fission fusion A produces larger nuclei is the energy source of a star B produces larger nuclei releases energy in a power station C produces smaller nuclei is the energy source of a star D produces smaller nuclei releases energy in a power station

8 24 Which graph shows how the count rate of a radioactive isotope varies with time? A B C D 25 For which purpose is the radioactive isotope carbon−14 used? A dating of ancient bones B fuel for a nuclear power station C killing cancerous cells D operating mobile telephones 26 When dealing with radioactive materials there are possible dangers. Which statement is correct? A Beta-particles can pass through skin and damage body cells. B Materials that emit only alpha-particles must be kept in thick lead containers. C Radioactive materials are safe to handle after two half-lives. D Sources of gamma radiation are dangerous because they have long half-lives. 27 An isotope X is radioactive and has a half-life of 4 years. A sample initially contains 8000 atoms of X. After how many years will the sample contain 1000 atoms of X? A 4 B 8 C 12 D 16

9 28 What is the safest way to dispose of a large quantity of highly radioactive waste? A burning it on a fire B burying it in dry rock deep underground C pouring it down the drain D pumping it into a river 29 The count rate from a radioactive material fal