RP12-Inverse square law

• Equipment: Gamma source, Geiger counter, ruler, stopwatch.
• Set up: With the geiger counter far from the source, start the stopwatch and use the geiger counter to record the total count reading after twenty minutes to determine background count. Then align the geiger counter with the gamma source.
• Method: Record the count after one minute and repeat for different distances of the source from the geiger counter. Repeat the experiment twice more and record the mean count for each distance.
• Graph: Plot a graph of 1/root(C') against X. This should be a straight line through the origin, verifying the inverse square law.
• Analysis: Calculate count rate using C = N/t and do the same for background count rate. Calculate corrected count rate, C' by subtracting background count rate from C.
• Safety: Radiation destroys cells and causes mutations - do not touch the source, point it at somebody or go near it, keep it in a lead lined container when not in use.