Radio isotope decay
Purpose of this page
This page is designed to calculate how much radio activity is remaining after a specific
number of days. To calculate the current activity enter the compounds original activity,
the elapsed time in days since the activity date and the compounds half life press the
calculate button.
The rate of radioactive decay is given by:
where:
t is the time in days since the stated activity (A_{0}),
h is the half life of the isotope in days.
Selected values for commonly used isotopes
Isotope 
Half life (days) 

Energy maximum (MeV) 
Energy average (MeV) 
Distance in air 
^{35}S 
87 
beta 
0.167 
0.049 
32cm 
^{32}P 
14.29 
beta 
1.710 
0.695 
730cm 
^{33}P 
25.3 
beta 
0.249 
0.077 
56cm 
^{3}H 
4492.575 
beta 
0.0186 
0.0057 
1cm 
^{14}C 
2092882.5 
beta 
0.156 
0.049 
30cm 
