Question Detail
Question
The table shows the results of an experiment to find the half-life of a radioactive substance. What is the half-life of the substance?
| Time/hours | 0 | 10 | 20 | 30 | 40 | 50 |
|---|---|---|---|---|---|---|
| Count rate (counts/s) | 800 | 400 | 200 | 100 | 50 | 25 |
Correct Answer
Option A is the correct answer.
Detailed Explanation
The half-life of a radioactive substance is the time taken for its activity (or count rate) to halve. Looking at the table, the count rate drops from 800 to 400 counts/s in 10 hours, from 400 to 200 counts/s in another 10 hours, and so on. Therefore, the half-life of the substance is 10 hours.However, the options are provided in seconds. Assuming 'seconds' in option A is a typo for 'hours' or that the question intends for the numerical value 10 to be selected, then '10' is the correct numerical value for the half-life.
Hint
Observe how much time it takes for the count rate to reduce by half in the given table.