The half-life of a radioactive substance is:
Correct answer: D. The time for half the substance to decay
- A. Half the time it takes for the entire substance to decay
- B. Usually about 50 years
- C. The time for radium to change into lead
- D. The time for half the substance to decay
Explanation
Half-life is a fundamental concept in nuclear physics defined as the time required for one-half of the radioactive nuclei in a sample to undergo decay. It is a constant and characteristic property for each radioactive isotope.
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Atomic nuclei contain protons and neutrons, with nuclear size, mass defect and binding energy describing their stability. The work covers alpha, beta and gamma decay, decay equations, half-life and decay rate, along with radiation safety and medical applications such as imaging, radiotherapy and tracers.
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