5.2.1. Detection of radioactivity
A subsection of Physics, 5054, through 5. Nuclear physics
Listing 10 of 53 questions
One source of background radiation is cosmic rays. The cosmic rays that enter the Earth’s atmosphere are known as primary cosmic rays. Most of these rays are fast-moving protons or fast-moving alpha-particles. Both the Earth’s magnetic field and the Earth’s atmosphere reduce the number of primary cosmic rays that reach the Earth’s surface. Name a source of background radiation apart from cosmic rays. State one effect of background radiation. State the number of protons and the number of neutrons in an alpha-particle. number of protons number of neutrons Explain how the Earth’s atmosphere reduces the number of alpha-particles that reach the surface. shows an area where there is a uniform magnetic field into the page. On , draw a diagram to show the deflection of an alpha-particle by this magnetic field. magnetic field into page Primary cosmic rays produce carbon-14 in the atmosphere. The half-life of carbon-14 is 5700 years. Define the term half-life. A specimen of wood is found to contain 25 000 atoms of carbon-14. An otherwise identical specimen taken from a living tree is found to contain 200 000 atoms of carbon-14. Determine the age of the specimen that contains 25 000 atoms of carbon-14. age = State why it is not possible to use the amount of carbon-14 to date a specimen that is 570 000 years old. Carbon-14 is one of the isotopes of carbon. Another isotope is carbon-12. Describe how a nucleus of carbon-14 differs from a nucleus of carbon-12. Describe one similarity in the structure of the nuclei of these isotopes.
5054_s17_qp_22
THEORY
2017
Paper 2, Variant 2
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A smoke detector contains a small radioactive source of americium-241. The source emits alpha-particles. In the space below, draw a diagram of an apparatus that can be used to show that the source emits alpha-particles. Describe how this apparatus is used. Explain how the results of the test show that the source emits alpha-particles. The smoke detector works because alpha-particles from the source ionise the air. Compare the relative ionising effects and penetrating powers of alpha-particles, beta-particles and gamma rays. ionising effects penetration effects Americium-241 has a half-life of 430 years. Radium-224 is another element that emits alpha-particles. It has a half-life of 3.6 days. Explain why americium-241 is more suitable as the radioactive source in a smoke detector than radium-224. A smoke detector contains 8.0 × 1011 atoms of americium-241. Calculate the time taken for the number of atoms of americium-241 to fall to 1.0 × 1011. time = When used correctly, the radioactive source in the smoke detector is less harmful than background radiation. State one harmful effect of background radiation. A radioactive source is picked up using a long-handled tool. Explain why this is safer than using a short-handled tool.
5054_s18_qp_22
THEORY
2018
Paper 2, Variant 2
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A sample of a radioactive isotope with a very long half-life is placed next to a detector. Sheets of different materials are inserted, one at a time, between the radioactive sample and the detector. The background count rate is subtracted from the readings on the detector and the corrected count rates are recorded in the table. type of material corrected count rate counts / s no sheet inserted thin aluminium sheet thin lead sheet thin paper sheet Which types of radiation are emitted by the radioactive sample?
5054_s23_qp_12
MCQ
2023
Paper 1, Variant 2
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A radioactive source emits α-particles, β-particles and γ-radiation. State which type of radiation produces the strongest ionising effect. State which type of radiation is deflected most by a magnetic field. shows a Geiger-Müller (G.M.) tube and counter. A radioactive source is placed 10 cm from the G.M. tube. In a piece of metal 5 mm thick is placed between the source and the G.M. tube. The readings on the counter have been corrected for background radiation and show the count rate due to the source. 10 cm counter radioactive source G.M. tube 5 mm thick metal Explain how the readings show that the source emits β-particles and γ-radiation. State why the readings cannot be used to show that the source emits α-particles. Describe one way that a radioactive source is moved safely in a school laboratory.
5054_s23_qp_22
THEORY
2023
Paper 2, Variant 2
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Table 7.1 shows four different nuclei. Table 7.1 thorium-236 protactinium-236 uranium-235 uranium-238 90Th 91Pa 92U 92U State which two nuclei have the same number of protons. State which two nuclei have the same number of neutrons. State which two nuclei have the same number of nucleons. A teacher uses a Geiger-Müller tube and a counter to measure the background radiation in the laboratory. The counter records 20 counts per minute. A radioactive source is then placed in front of the tube and the counter records 420 counts per minute. State what is meant by ‘background radiation’. The measured count rate of 420 counts per minute can be corrected for background radiation. Calculate the corrected count rate from the source. count rate = counts per minute The radioactive source has a half-life of 45 minutes. Determine the reading on the counter 90 minutes later. reading on counter = counts per minute Suggest why your answer to is only an estimate. shows different uses of three different types of radiation. Draw a line on from each use of radiation to the type of radiation used. One line has been drawn for you. Each type of radiation can be used once, more than once or not at all. use of radiation type of radiation a-particle household fire alarm irradiating food to kill bacteria sterilisation of equipment measuring paper thickness b-particle c-radiation
5054_s24_qp_21
THEORY
2024
Paper 2, Variant 1
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is a half-scale diagram of a radioactive source stored in a safe way. The source emits alpha-particles, beta-particles and gamma-rays. A teacher handles the box. Explain how the teacher is completely protected from the alpha- and beta-particles but only partially protected from the gamma-rays. Describe and explain how the teacher should remove the source from the box safely. The source is brought near a radiation detector. Name a suitable detector. Describe how you would use the detector to show that the source emits particles at random. wooden outer box with hinged lid hinge lead inner container source Use
5054_w05_qp_2
THEORY
2005
Paper 2, Variant 0
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Questions Discovered
53