Creative Education
2012. Vol.3, No.5, 671-673
Published Online September 2012 in SciRes (http://www.SciRP.org/journal/ce) http://dx.doi.org/10.4236/ce.2012.35099
Copyright © 2012 SciRes. 671
Radioactive Branching Using Dice
Sarmistha Sahu
Department of Physics, Maharani Lakshmi Ammanni College for Women, Bangalore, India
Email: sarmistha.sahu@gmail.com
Received July 7th, 2012; revised August 12th, 2012; accepted August 22nd, 2012
Dice rolling (Emeric, 1997) is a useful pedagogical tool (Arthur & Ian, 2012; Todd, Clifton, Ingrid, &
Zdravko, 2006) to introduce students to the concepts and essential features of radioactivity. It can be ex-
tended to explain radioactive branching. In the process, the students learn about half life, decay constant
and activity of a radioactive substance. Terms like stochastic processes, probability of decay, statistical
fluctuations, and mutually exclusive processes; becomes clear in this process.
Keywords: Radioactivity; Probability; Transition Rate; Half Life; Radioactive Branching
Introduction
Dice rolling is being used as a pedagogical tool in schools as
well as undergraduate studies in physics, mathematics, statistics
and computer science curriculum. Students learn while they
play. Todd W. Neller et al. has used dice rolling in a dice game
Pig (Todd, Clifton, Ingrid, & Zdravko, 2006) for undergraduate
research in machine learning. Arthur Murray et al. mention that
“the ‘radioactive dice’ experiment is a commonly used class-
room analogue to model the decay of radioactive nuclei” (Ar-
thur & Ian, 2012). Simple dice rolling can unfold important
concepts elegantly.
Theory
Some radionuclides may have several different paths of de-
cay. For example, approximately 36% of Bismuth-212 decays
through alpha-emission to thallium-208 while approximately
64% of Bismuth-212 decays through beta-emission to Polo-
nium-212. Both the Thallium-208 and the Polonium-212 are
radioactive daughter products of Bismuth-212 and both decay
directly to stable Lead-208 (Tayal, 1988).
If a nucleus can decay by several different processes for
which the probabilities per unit time are λ1, λ2, λ3, ··· then the
total probability λ per unit time for decay is
123
and the half lives are related as
123
12 12 1212
11 11
TT TT
where
1
12
T is the half-life if only process 1 was available
and so on. These are called the partial half-lives. If one of them
is shorter than the others then it is dominant in determining
12
T.
Experiment
Dice Used
About 100 cuboctahedron (truncated cubes with 6 square
faces and eight triangular faces) have been used for the experi-
ments (Figure 1). In this experiment one of the six square faces
(suitably marked) and all of the triangular faces represent two
unstable states. The unmarked five square faces represent the
stable state of radioactive nuclei.
The dice represents a radioactive nucleus having many en-
ergy states. One of the states is represented by the yellow-
square-face. Eight of the triangular faces represent yet another
energy state. All the eight states have the same energy (degen-
erate states). Five of the unpainted square faces represent an-
other energy state.
Experimental Procedure
By rolling the dice a large number of times quantify the
probability per throw of yellow square face “up” (λ1) and any
red triangular face “up” (λ2). (In this experiment λ1 is smaller
than λ2.) Let the yellow square face “up” represent the alpha
decay and any red triangular face “up” represent the beta decay.
For each throw t (0, 1, 2, ···), start with Nt number of dice,
roll and remove the decayed nuclei (die with the specified face
“up”). Continue with the remaining un-decayed dice till about
ten percent of the dice is left. The entire process is repeated
once for alpha decay (Figure 2), once for beta decay (Figure 3)
and once for both the processes together (Figure 4).
Figure 1.
Truncated Cube (Cuboctahedron) with three types of
faces made from 3 cm wooden cubes.