5.2. Radioactivity
A subsection of Physics, 5054, through 5. Nuclear physics
Listing 10 of 187 questions
A radioactive source is placed 3 cm from a Geiger-Müller tube in air. The average count rate is 742 counts / minute. source Geiger-Müller tube counter Then, in three experiments, measurements are taken with sheets of different materials placed between the source and the tube. The results are recorded in the table. material of sheet between source and tube thin card aluminium foil thick lead average count rate / counts per minute Which types of radiation does the source emit?
5054_s05_qp_1
MCQ
2005
Paper 1, Variant 0
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A scientist has three radioactive sources. The first source emits only alpha-particles, the second source emits only beta-particles and the third source emits only gamma-rays. Explain how the scientist demonstrates that the three types of radiation have different penetrating powers. In your account • draw a diagram of the apparatus used, • state what materials are used to show the different penetrating powers, • explain how the apparatus is used. State two different safety precautions the scientist must follow when handling the radioactive sources. Explain why the half-lives of the radioactive sources used in the demonstration should be greater than 1 second. shows radiation moving into the magnetic field between the poles of a strong magnet. N S radioactive source radiation The radioactive source emits alpha-particles, beta-particles and gamma-rays. For each type of radiation, describe the path taken by the radiation. You may draw a diagram to help your explanation. represents three different nuclei. nucleus A nucleus B nucleus C neutron proton State and explain which nuclei are from different isotopes of the same element.
5054_s08_qp_2
THEORY
2008
Paper 2, Variant 0
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shows part of a smoke detector. + – + – + – + – + – to alarm positive metal plate alpha- particles radioactive source negative metal plate (not to scale) Alpha-particles from the radioactive source ionise the air between the metal plates. There is then a small current in the resistor. When smoke enters the detector, the current changes and the alarm sounds. Explain why a source emitting only gamma-rays is unsuitable for use in the smoke detector. There is an electric field between the metal plates. On , draw the electric field between the plates. The alpha-particles in are deflected slightly as they pass through the electric field. Explain why the alpha-particles are deflected and state the direction of the deflection. State and explain how the path of gamma-rays differs from the path of alpha-particles as they pass through an electric field. The source used is the radioactive isotope americium-241, which has a half-life of 500 years. A sample of americium-241 is left for 1500 years. Determine the fraction of the original number of atoms of americium-241 left in the sample after this time. fraction = Another isotope of the same element, americium-242, has a half-life of 16 hours. Explain why the half-life of americium-242 makes this isotope unsuitable for use in a smoke detector. Atoms of americium-241 and americium-242 contain protons, neutrons and electrons. 1. State two similarities in the structure of an atom of americium-241 and an atom of americium-242. 2. Describe the difference between an atom of americium-241 and an atom of americium-242.
5054_s12_qp_21
THEORY
2012
Paper 2, Variant 1
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Questions Discovered
187