What will happen in a time of 7 hours, if a radioactive substance has an average life of 7 hours?
Correct answer: C. More than half of the active nuclei decay
- A. Half of the active nuclei decay
- B. Less than half of the active nuclei decay
- C. More than half of the active nuclei decay
- D. Total nuclei decay
Explanation
Option A) Half of the active nuclei is incorrect because the half-life is defined as the time it takes for half of the active nuclei to decay. So, after one half-life, half of the active nuclei will decay. Option B) Less than half of the active nuclei decay is incorrect because the half-life is defined as the time it takes for half of the active nuclei to decay. So, after one half-life, half of the active nuclei will decay.Option C) The mean life of an element equals the half-life of the substance divided by the natural logarithm of 2 which is about 0.693. Since the entire radioactive nuclei can never decay, more than half of the nuclei will decay.Option D) Total nuclei decay is incorrect because radioactive decay is a random process and cannot be predicted with certainty. However, the concept of half-life allows us to make statistical predictions about the decay process.
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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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