5.2.5. Half-life
A subsection of Physics, 5054, through 5. Nuclear physics
Listing 10 of 45 questions
11 Complete the table of . type of radiation nature of radiation charge alpha-particle two protons and two neutrons positive beta-particle gamma-ray Technetium-99 is a radioactive isotope that emits gamma-rays and it has a half-life of 6.0 hours. In a hospital, a solution containing this isotope is injected into a patient. The solution travels around the body and the isotope attaches to cancer cells. A few hours after the injection, an instrument is used to detect the gamma-rays emitted by the isotope. A high reading on the instrument indicates the position of cancer cells. Explain what is meant by half-life. Explain why an isotope emitting gamma-rays is used rather than an isotope emitting alpha-particles. Explain why using an isotope with a half-life of 6 hours is better than using an isotope with a half-life of 6 minutes. Explain why using an isotope with a half-life of 6 hours is better than using an isotope with a half-life of 6 days. A different radioactive isotope used in hospitals has a half-life of 13 hours. A sample of this isotope and a detector are placed in a lead box. The count rate is recorded every minute for three minutes. The values obtained are 3202, 3140 and 3258 counts per minute. Explain why the three readings are not the same. Estimate the time taken for the average count rate to fall to 200 counts per minute. time taken = The sample and the detector are taken out of the lead box. The count rate rises slightly because of background radiation. State one cause of background radiation.
5054_s10_qp_21
THEORY
2010
Paper 2, Variant 1
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An atom consists of electrons surrounding a nucleus made up of protons and neutrons. State which of these particles have an equal and opposite charge, have almost equal mass. The nuclide notation for carbon-14 is 14 6C. Carbon-14 decays by beta emission to a stable isotope of nitrogen (N). Write numbers in the empty boxes below to show the nuclide notation for this isotope of nitrogen. 6C N + β The half-life of carbon-14 is 5700 years. A sample of wood from a living tree contains 2.4 × 1012 atoms of carbon-14. A similar sample of the same size is taken from an old piece of wood. It contains 6.0 × 1011 atoms of carbon-14. Calculate the age of the old piece of wood. age =
5054_s14_qp_22
THEORY
2014
Paper 2, Variant 2
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Questions Discovered
45