Introduction

This simulation models half-life using red nuclei that decay to blue. There are two modes: 'Continuous' and 'Step-wise'. 'Continuous' lets you view and graph nuclear decay; the decay model is truly random, so each run will be slightly different and you will see realistic noise and messiness in the data. 'Step-wise' lets you advance time in steps to explore the maths without the randomness.

Getting started

• Select 'Continuous' or 'Step-wise' from the mode toggle.

Continuous mode

• Click 'Start' to begin decay and 'Reset' to reset it.
• Use the 'Half-life' slider to choose a half-life between 1 s and 60 s.
• Adjust the 'Number of atoms' slider to change the square of atoms from 1 x 1 (1 atom) up to 100 x 100 (10,000 atoms).
• Toggle 'Show graph' to display a graph of the decay.
• Toggle 'Data type' between 'Atoms' (atoms remaining) and 'Decay' (decay rate).
• Toggle 'Graph type' between 'Line' and 'Scatter'.
• Tick 'Curve of best fit' to display the fit line.
• Tick the 'Half-life' checkboxes to show each half-life.
• Click 'Export' to copy a graph image or download a CSV of decay data.
• Click 'Full' to expand the graph to full-screen.
• Toggle 'Show radiation' to display particles emitted on decay.
• Toggle 'Show person' to display a person absorbing radiation. They safely absorb five units per second; above that, harm builds up until '100%' and the person dies.
• Tick 'Play click on decay' for a Geiger-style click each time an atom decays to represent a unit of radiation being detected.

Step-wise mode

• Click 'Ahead one step' or 'Back one step' to move in time.
• Toggle 'Step type' between 'Half-life' (one half-life per step) and 'Time' (choose a custom step up to two half-lives).
• Set 'Half-life' and 'Number of atoms' as in continuous mode.
• Set 'Number of undecayed atoms remaining' to adjust the proportions of undecayed and decayed atoms.