Using radioactivity: choose the source sim
For five jobs (a paper thickness gauge, a medical tracer, a smoke alarm, sterilising, dating) pick a source from a lead-lined box by its radiation and half-life, try it on a real bench by dragging the apparatus and looking again later, then commit; also sort four cases into irradiated or contaminated.
Radioactivity: uses, safety, irradiation and contamination · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Model: each source is chosen by what its radiation gets through (α stopped by paper or a few cm of air, β by a few mm of aluminium, γ only reduced by thick lead) and by its half-life (activity left = (1/2)^(t ÷ T½)). Every source starts equally strong, and the absorption numbers, counts, currents and dose rates are illustrative (see the box below the table). Counts scatter by about √N. Nothing runs on its own: readings change only when you move something or choose a source or a time.
- The part you move: the handwheel, the camera head, the incense holder, the box of syringes or the sample tray
- The bench for each job, with the lead-lined source box and long tongs
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
More physics sims
- Efficiency: a motor lifting a load simSet the supply's voltage and the load, then time a small geared motor winding a slotted-mass load up beside a half-metre rule: read the energy in from a joulemeter (or V × I × t), work out the useful energy m g Δh and the efficiency, watch a Sankey diagram of where the energy went draw itself, and plot how the efficiency changes with the load.
- Electric field patterns simSwitch on an EHT supply joined to electrodes in a dish of castor oil and watch semolina grains line up into the field pattern of a point, a charged sphere, two points or two parallel plates; drag the electrodes, show field lines running from + to −, and drop in a small + or − test charge to see the force on it.
- Energy resources: power a town simDrag the faders on a model town's control desk to switch on coal, gas, nuclear, biofuel, geothermal, hydroelectric, wind, solar and tidal power, change the wind, the sky and the hour, and see hour by hour whether the supply meets the town's demand, with scores for hours met, CO₂, renewables and rough cost; save your mixes to a table and sort the resources by renewable, from the Sun and available at any hour.
- Evaporation and boiling simWeigh a dish of water or ethanol on a balance as it evaporates, changing the temperature, the surface area and a desk fan's air speed; watch a wet-bulb thermometer cool below a dry one; then heat water on a hotplate until bubbles form all through it and the temperature stays at the boiling point.
- Floating, sinking and upthrust simLower a cylinder on a newton-meter into water, salt water or cooking oil from a displacement can that spills into a beaker on a balance: watch the reading fall as the upthrust grows, find U = weight in air − reading in the liquid, predict float or sink from the densities, and see a wooden block float deeper in oil and higher in salt water; cards show a hydrometer and a steel boat.
- Magnetic field of bar magnets simPlot the field round a bar magnet the classic way, moving a plotting compass and marking a pencil dot at each end of its needle, then sprinkle iron filings, put two magnets N–N (finding the neutral point X) and N–S, and add the Earth's field to see where it cancels the magnet's.