- can be measured using *Geiger muller (GM counter).
in 1 type of GM counter
- detector, counter, display are single unit
other type:
- detector connected to counter
SI unit of amt of radioactivity: Becquerel (Bq)
1 becquerel = 1 disintegration per second
- refers to amt of ionising radiation released when a radioactive atom spontaneously emits electromagnetic radiation as a result of the radioactive decay
Measurement of radiation → sometimes expressed as being a rate of counts per unit time → known as count rate
- can be measured using GM counter
units: counts/min or counts/s
Steps to measure background radiation. (require GM counter and stopwatch)
- remove all known radioactive sources
- start counter and stopwatch
- stop counter after 10 mean and record number of counts
- number of counts per minute =
- repeat measurement at least 2 times and calculate mean
can also record number of counts for longer time interval - e.g. 20min
longer time - counts/min shorter time - counts/s
when doing experiments with radioactive sources → always measure background radiation. subtract this background count rate from measurements to obtain corrected count rate for radioactive source