5.2.1. Detection of radioactivity
A subsection of Physics, 5054, through 5. Nuclear physics
Listing 10 of 53 questions
shows the proton number and the nucleon number of the nuclei of five neutral atoms. neutral atom 1 neutral atom 2 neutral atom 3 neutral atom 4 neutral atom 5 proton number nucleon number State the two atoms in that are different isotopes of the same element, contain the same number of neutrons, contain the same number of electrons. The nucleus of atom 1 is radioactive and when it decays, it emits a beta-particle. State, for the nucleus produced by this decay the proton number, proton number = the nucleon number. nucleon number = A sample contains a large number of radioactive nuclei that emit beta-particles. The sample is placed near to a radiation detector in a laboratory and the count rate is recorded over a long period of time. shows the count rate recorded by the detector during this period. time / days count rate counts / minute Suggest two major sources of background radiation. 1. 2. Using , 1. determine a value for the background count rate in the laboratory, background count rate = 2. determine the count rate, at time = 0, due to the sample on its own, count rate due to sample = 3. estimate the half-life of the radioactive atoms in the sample. half-life = A student suggests a change to the experiment in . He suggests completely encasing the radiation detector in lead before the sample that emits beta-particles is placed near to it. The effect on the count rate of background radiation may then be ignored. Describe and explain the effect on the background count rate recorded by the detector of completely encasing the radiation detector in lead. State and explain whether the student’s suggestion is a sensible one.
5054_w15_qp_21
THEORY
2015
Paper 2, Variant 1
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The proton number (atomic number) of the element lead is 82. The isotope lead-209 (209 82Pb) is radioactive and decays by the emission of beta-particles. Describe the composition and structure of a neutral atom of lead-209. A nucleus of lead-209 emits a beta-particle. State how the composition of the nucleus produced differs from the original nucleus. Complete the table in to show the relative ionising effects of the three types of ionising radiation produced by radioactive decay. least strongly ionising most strongly ionising A sample containing lead-209 nuclei is used to produce a beam of beta-particles. The beta-particles enter a magnetic field. The magnetic field is perpendicular to the direction of travel of the beta-particles. The beta-particles travel from left to right. shows that the direction of the magnetic field is out of the page. magnetic field out of the page beam of beta-particles On , sketch the path of the beta-particles in the magnetic field. An industrial technician uses a detector to measure the background count rate in a laboratory. State what is meant by background radiation. Suggest two major sources of background radiation. 1. 2. The average reading for the background count measured by the technician is 16 counts / minute. He then brings a sample that contains a radioactive isotope of lead close to the detector and he finds that the new count rate is 92 counts / minute. The half-life of this isotope is 3.3 hours. Determine the count rate measured using the detector after 6.6 hours. count rate =
5054_w15_qp_22
THEORY
2015
Paper 2, Variant 2
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shows a radiation detector placed on a laboratory bench. 000031 counts / minute radiation detector point P The detector is switched on and six readings of the count rate are recorded. The table in shows the readings obtained. reading number count rate counts / minute Using all the readings obtained, determine an average value for the background count rate. background count rate = shows a point P which is a very short distance from the end of the radiation detector. A sample of the radioactive isotope cobalt-60 is placed at P. The average value of the count rate obtained is now 975 counts / minute. The average count rate is determined with different objects between the radiation detector and the sample. The table in shows the results obtained. object average count rate counts / minute no object four sheets of paper 0.50 mm thickness sheet of aluminium 2.0 cm thickness sheet of lead Indicate, by placing ticks (✓) in the appropriate boxes, the radiation emitted by cobalt-60. alpha-particles beta-particles gamma rays This radiation is produced when a nucleus of cobalt-60 ( 60 27Co) decays into a nucleus of the daughter product X. Product X is not radioactive. Determine 1. the number of protons in a nucleus of X, number of protons = 2. the number of neutrons in a nucleus of X. number of neutrons = The half-life of cobalt-60 is 5.3 years. State what is meant by half-life. When there is a lead sheet between the detector and the sample, the average count rate is obtained from six readings taken at one-minute intervals. The six readings are given in the table in . reading number count rate counts / minute There are reasons for suggesting that the variation in these readings is random and not because the number of cobalt-60 atoms in the sample is decreasing. State two of these reasons. 1. 2.
5054_w18_qp_22
THEORY
2018
Paper 2, Variant 2
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The isotope yttrium-90 ( 90 39 Y ) is radioactive. It is a beta-particle emitter that decays to product Q. Product Q is stable. State one feature that is common to all isotopes of yttrium. Describe how a neutral atom of Q differs from a neutral atom of yttrium-90. A sample of yttrium-90 is placed close to a radiation detector in a laboratory. There are no other radioactive samples in the laboratory. A counter records the count rate. is a graph of the count rate plotted against time. time / s time / hours count rate counts / minute Using , determine the average background count rate. average background count rate = Suggest two different origins for the background count. 1. 2. Using , determine the half-life of yttrium-90. Show how the answer is obtained. half-life = Many of the points plotted in do not lie on the best-fit line. Explain why. A beam of beta-particles, travelling in a vacuum, enters the region between two parallel, metal plates. One plate is negatively charged and the other is positively charged. shows the arrangement. beam of beta-particles + + + + + + – – – – – – On , draw the path taken by the beta-particles as they travel between the two plates.
5054_w21_qp_21
THEORY
2021
Paper 2, Variant 1
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During a radioactivity experiment, the background reading is 28 counts per minute. A radioactive source is placed 2 cm in front of a detector which is connected to a counter. 2 cm source detector sheet to counter Counter readings are taken with and without sheets of different materials placed between the source and the detector. type of sheet reading / counts per minute no sheet thin card 5 mm thick aluminium Which types of radiation are being emitted by the source?
5054_w24_qp_12
MCQ
2024
Paper 1, Variant 2
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Questions Discovered
53