Practice Quiz

Praxis II General Science

Category - Major Ideas

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Which of the following statements about radioactivity is not true?
  1. The number of radioactive particles in a sample is directly proportional to the activity of that sample.
  2. If the half-life of a sample is 10 years, then after 20 years only 25% of the sample will remain.
  3. Over time, the radioactivity of a sample will increase.
  4. Alpha, beta, and gamma are the three main types of radioactive decay.
  5. All of the above are true.
Explanation
Answer: C - Radioactivity does not increase over time, and instead decreases as the sample mass is lost. You would expect that after 1 half-life, the number of radioactive particles would halve, and result in about half the radiation.
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