Posted by **Judy** on Saturday, November 17, 2007 at 12:41pm.

A certian radioactive isotope has a half-life of 1 hour. If you start with 1 gram of the material at noon, how much of the original isotope will the sample contain at 3 pm? At 6 pm? At 10 pm?

- Physics -
**Michael**, Saturday, November 17, 2007 at 1:09pm
A half-life is how long it takes for a radioactive isotope to decay by half.

At 2 PM, you will have .5 grams of the material.

Each hour thereafter, divide the material by half to see how much remains.

- Physics -
**bobpursley**, Saturday, November 17, 2007 at 3:02pm
A better way is with the exponential function on your calculator.

Amountremaining= Originalamount* e^(-.692t/halflife)

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