If only 50% of the original amount of a radioisotope remains,
half the time has gone by
after twice that time there will be nothing left
the radioactivity has reached a safe level
a half-life has passed
To answer this question, you need to understand the concept of half-life. The half-life of a radioisotope is the amount of time it takes for half of the original amount to decay. Here's how you would calculate the time it takes for a radioisotope to reach various stages based on the given information:
1. If only 50% of the original amount remains, that means one half-life has passed. Therefore, you can conclude that the time it took for this to happen is the half-life of the radioisotope.
2. If twice the half-life has passed, that means two half-lives have passed. In this case, the radioisotope would have decayed to 25% (50% divided by 2) of the original amount.
3. To determine when there will be nothing left, you need to keep track of how many half-lives have passed. If the radioisotope decays by half after each half-life, you can continue dividing the remaining amount by 2 until it reaches zero. For example, after three half-lives, the radioisotope would be at 12.5% (25% divided by 2) of the original amount. After four half-lives, it would be at 6.25% (12.5% divided by 2), and so on. Eventually, after a sufficient number of half-lives, the remaining amount will become negligible, and you can consider it as nothing left.
4. When the radioactivity has reached a safe level, it means that the remaining amount of the radioisotope has decayed to a point where it is no longer considered dangerous. The exact threshold for a safe level depends on the specific radioisotope. You would need to consult radiation safety guidelines or experts to determine what is considered safe for a particular radioisotope.
In summary, by understanding the concept of half-life and performing calculations based on the given information, you can determine the time it takes for a radioisotope to reach various stages of decay.
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better review what a half-life is.