5.2.4. Half-life
A subsection of Physics, 0625, through 5. Nuclear physics
Listing 10 of 91 questions
Radioactive sources emit α-, β-and γ-radiations. State which of these types of radiation can pass through paper. Barium-137 is a radioactive isotope. The nuclide notation for barium-137 is 56Ba Determine the number of neutrons in a nucleus of barium-137. number of neutrons = An isotope of barium-137 has a half-life of 3 minutes. A radioactive source contains 36 mg of this isotope. Calculate the mass of the isotope that remains in the source after 9 minutes. mass of the isotope remaining = mg
0625_s20_qp_31
THEORY
2020
Paper 3, Variant 1
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shows a beam of radiation in a vacuum. The beam contains α-particles, β-particles and γ-rays. region of uniform magnetic field out of the page beam of radiation, containing α, β and γ-rays The beam enters a region where there is a strong, uniform magnetic field. The direction of the magnetic field is out of the page. On , mark and label the paths through the magnetic field of: α-particles (label this path α) β-particles (label this path β) γ-rays (label this path γ). Radioactive sources have many uses in medicine. State two safety precautions which hospital staff take when working with γ-ray sources. 1. 2. The radioactive isotope iodine-131 is used as a tracer in medical diagnosis. A nucleus of iodine-131 contains 53 protons and 78 neutrons. The symbol for iodine is I. Use nuclide notation to show this isotope of iodine. Iodine-131 emits γ-radiation. It has a half-life of 8 hours. Explain why this emission and this half-life make iodine-131 a suitable material for a tracer in medical diagnosis.
0625_s21_qp_43
THEORY
2021
Paper 4, Variant 3
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shows a tube for producing cathode rays. The tube contains various parts. A spot is formed on the screen by the cathode rays. What do cathode rays consist of? Which part, A, B, C or D, must be heated to create the cathode rays? Which part, A, B, C or D, is coated with fluorescent material? What is the purpose of the fluorescent material? A potential difference is applied between the two halves of part C. What effect does this have on the cathode rays? Explain why there needs to be a vacuum inside the tube. A B C D Use
0625_w05_qp_2
THEORY
2005
Paper 2, Variant 0
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State the nature of γ-rays. A nucleus of technetium-99 (99 43Tc) emits only a γ-ray. State any effect of this on the proton number of the nucleus, the nucleon number of the nucleus. In a laboratory a radiation detector displays a count rate of 16 counts / minute due to background radiation. State what is meant by background radiation. A sample of a radioactive isotope is placed near to the radiation detector and a count rate of 112 counts / minute is recorded. After 18 hours, the count rate recorded is 28 counts / minute. Determine the half-life of this isotope. half-life = Radioactive isotopes are stored in thick lead containers. State two precautions to be taken when radioactive isotopes are used. 1. 2.
0625_w17_qp_43
THEORY
2017
Paper 4, Variant 3
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A nuclear power station uses uranium to generate thermal energy. The fuel for the power station is an isotope of uranium. Explain the meaning of the term isotope. When the nucleus of a uranium atom decays, it releases a β-particle. Describe the relative ionising effect, and the relative penetrating ability, of a β-particle. relative ionising effect relative penetrating ability A sample of rock includes some uranium-239. The half-life of uranium-239 is 23 minutes. Determine the fraction of the uranium-239 that remains after 46 minutes. fraction remaining =
0625_w18_qp_33
THEORY
2018
Paper 3, Variant 3
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State two differences between nuclear fission and nuclear fusion. Radioactive tracers emitting γ-rays can be used in medicine. The half-life of the source of these γ-rays is 6 hours. Explain why a source of γ-rays used in this way should not have a half-life shorter or longer than about 6 hours. Technetium-99 is a source of γ-rays often used as a radioactive tracer. It is produced from molybdenum-99 which emits β-particles. The symbol for technetium is Tc and the symbol for molybdenum is Mo. Complete the nuclide equation for this decay. 42 Mo Tc + β Technetium-99 is a radioactive nuclide. State another use of radioactive nuclides in medicine.
0625_w20_qp_42
THEORY
2020
Paper 4, Variant 2
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Questions Discovered
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