The count rate of an alpha-particle source is 400 per minute. If the half-life of the source is 5 days, what would be the count rate per minute after 15 days?

Johnnne

2 years ago

The correct answer is C. 50.

The half-life of the source is 5 days, which means that every 5 days, the count rate will decrease by half.

After 5 days, the count rate will be:
400 / 2 = 200

After 10 days (two half-lives), the count rate will be:
200 / 2 = 100

After 15 days (three half-lives), the count rate will be:
100 / 2 = 50

So, the count rate per minute after 15 days is indeed 50.

Here's a brief summary:

- 5 days: 400 → 200
- 10 days: 200 → 100
- 15 days: 100 → 50

The correct answer is C. 50.