Nuclear Decay Revisited

Enter the probability to decay in a time unit – approximately 0.083 for Iodine 131 to decay in one day. Also make a row of day numbers 0 to 30.

Enter 1000 1’s (shown in Col B below) and Sum them at the top of the column under the Day numbers.

Use IF and RAND() to simulate decay (a change from 1 to 0).

Copy the formula down. (Get the “thin cross” and double click.)

Copy the sum formula over. You should see about 8.3% of the “atoms” decayed.

Copy the formula for the simulated atoms and the sum over for the 30 days.

Highlight the Day and Sum rows and make an XY Scatter graph.

Fit to an Exponential, label axes, title, etc.

Interpolation

• According to your fit formula, what percentage of atoms are left (un-decayed) after 8 days?

• 16 days? • 24 days?