5.2.5. Half-life
A subsection of Physics, 5054, through 5. Nuclear physics
Listing 10 of 45 questions
Table 10.1 contains details of the nature and some properties of alpha, beta and gamma emissions. Table 10.1 alpha beta gamma nature 2 protons and 2 neutrons charge negative penetrating power stopped by 5 mm of aluminium Complete Table 10.1 by filling in the missing details. Surgical instruments in sealed plastic bags are placed in thin plastic boxes. A conveyor belt takes the boxes close to a cobalt-60 source which sterilises the instruments. This is shown in . cobalt-60 source thick concrete boxes of surgical instruments conveyor belt (viewed from above) The cobalt-60 source is a radioactive isotope of cobalt that emits gamma-radiation. Describe what is meant by the term isotope. Suggest a property of gamma-radiation that enables it to sterilise the instruments in the bags in the boxes. State why a source emitting only alpha-radiation cannot be used in this way. The half-life of cobalt-60 is 5.3 years. Explain why a source with a half-life of 5.3 minutes is unsuitable for use in this application. Geiger and Marsden performed an experiment in which alpha-particles were fired at a thin film of gold. shows an alpha-particle passing close to the nucleus of a gold atom. path of alpha-particle nucleus of gold atom Explain why the alpha-particle is deflected. In the experiment, most of the alpha-particles pass straight through the foil without deflection. Explain, using ideas about the structure of the atom, why this happens.
5054_s21_qp_21
THEORY
2021
Paper 2, Variant 1
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Table 9.1 shows details of seven different nuclides. Table 9.1 nuclide radiation emitted half-life hydrogen-2 none − hydrogen–3 beta 12 year francium-223 beta 22 min iridium-192 gamma 74 day phosphorus-32 beta 14 day radon−222 alpha 4 day technetium-99 gamma 6 hour Hydrogen-2 and hydrogen-3 are isotopes of the element hydrogen. Define the term isotope. The equation for the decay of phosphorus-32 (P-32) as it emits a beta particle is: 15 P → 0 –1β + 32 16 Q Explain whether the equation shows that Q is another isotope of phosphorus. Q is not the chemical symbol for the atom. One of the sources in Table 9.1 is used in a medical procedure to detect unusual bone structures. It is injected into a patient and the radiation emitted is detected outside the body. State which source in Table 9.1 is most suitable for this type of medical use. Explain two reasons for your choice Radon gas is one natural source of background radiation. Some causes of background radiation are man-made, for example, X-rays. State one other natural source of background radiation. State one other man-made source of background radiation. State one harmful effect of background radiation. One fusion reaction that occurs is: 1H + 3 1H → 4 2He + X Complete the equation to show the missing proton and nucleon numbers. Deduce the name of particle X. Suggest where this fusion reaction takes place. Compare the properties of alpha-particles and beta-particles in terms of their: • ability to penetrate through materials • ionising effects • deflection in a magnetic field.
5054_s22_qp_21
THEORY
2022
Paper 2, Variant 1
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Sodium-24 and sodium-23 are two of the isotopes of sodium. Sodium-24 is a radioactive isotope that emits beta-particles and gamma-rays as it decays. The nuclide notation for the isotope sodium-24 is 2 1Na. Describe the composition and structure of a neutral atom of sodium-24. State how the composition of a nucleus of sodium-24 differs from the composition of a nucleus of sodium-23. A nucleus of sodium-24 decays. It emits a beta-particle and produces a nucleus of an isotope of magnesium (Mg). State the name of the particle that is identical to a beta-particle. Complete the nuclide equation for the emission of a beta-particle (β) by sodium-24. 1Na β + Mg When it decays, sodium-24 also emits gamma-rays. State what gamma-rays are. shows a beam of beta-particles and a beam of gamma-rays entering the electric field between two oppositely charged plates. beam of beta-particles beam of gamma-rays + + + + + + + + – – – – – – – – (not to scale) On , draw the path of the beta-particles in the electric field between the charged plates. On , draw the path of the gamma-rays in the electric field between the charged plates. Explain why the path taken by the beta-particles differs from that taken by the gamma- rays. Sodium-24 is sometimes used in diagnosing medical conditions. The half-life of sodium-24 is 15 hours. Explain one reason why a half-life of 15 hours makes the isotope suitable for use in the human body.
5054_w16_qp_21
THEORY
2016
Paper 2, Variant 1
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The isotope iodine-131 emits two types of nuclear radiation. Gamma radiation is one of the types emitted. A sample of iodine-131 produces a narrow beam of radiation which passes into a magnetic field. shows some of the paths taken in the magnetic field by the radiation emitted from the sample. sample magnetic field directed into page The direction of the magnetic field is into the page. On , mark with a gamma symbol (γ) any of the paths taken by the gamma radiation. Determine the other type of radiation emitted by iodine-131. Explain how you obtain your answer. type of radiation explanation In another experiment, the beam of radiation from the sample is incident on a 5 mm thick sheet of lead. State what happens to the two types of radiation in the beam. Question 10 continues over the page. The gamma radiation produced has a frequency of 8.8 × 1019 Hz. The speed of electromagnetic radiation in a vacuum is 3.0 × 108 m / s. Calculate the wavelength of this gamma radiation in a vacuum. wavelength = m
5054_w23_qp_22
THEORY
2023
Paper 2, Variant 2
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Questions Discovered
45