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Created page with "==Key Stage 4== ===Meaning=== '''Count rate''' is the number of particles of ionising radiation that reach a detector per second. ===About Coun..."
==Key Stage 4==
===Meaning===
'''Count rate''' is the number of [[particle]]s of [[Ionising Radiation|ionising radiation]] that reach a detector per [[second]].
===About Count Rate===
: The [[SI Unit]]s of [[Count Rate|count rate]] are [[Becquerel]]s (Bq).
: '''Count rate''' is measured using a [[Geiger Counter|Geiger counter]].
: The '''count rate''' at the detector will be less than the [[radioactivity]] of the [[sample]] of [[Unstable Isotope|unstable isotope]] because the [[Ionising Radiation|ionising radiation]] spreads out in all directions equally.
: The greater the distance from the [[radioactive]] [[sample]] the lower the [[Count Rate|count rate]].
: For an [[Alpha Particle|alpha]] source the [[Count Rate|count rate]] drops to 0 beyond 5cm because the [[Alpha Particle|alpha particle]]s are [[Absorb (Physics)|absorbed]] by a few [[centimetre]]s of [[air]].
: For a [[Beta Particle|beta]] source the [[Count Rate|count rate]] drops to 0 beyond a few [[metre]]s because the [[beta Particle|beta particle]]s are [[Absorb (Physics)|absorbed]] by the several [[metre]]s of [[air]].
: For a [[gamma-ray]] source the [[Count Rate|count rate]] drops at a rate of 1/r<sup>2<sup> where r is the distance between the source and detector.
===Meaning===
'''Count rate''' is the number of [[particle]]s of [[Ionising Radiation|ionising radiation]] that reach a detector per [[second]].
===About Count Rate===
: The [[SI Unit]]s of [[Count Rate|count rate]] are [[Becquerel]]s (Bq).
: '''Count rate''' is measured using a [[Geiger Counter|Geiger counter]].
: The '''count rate''' at the detector will be less than the [[radioactivity]] of the [[sample]] of [[Unstable Isotope|unstable isotope]] because the [[Ionising Radiation|ionising radiation]] spreads out in all directions equally.
: The greater the distance from the [[radioactive]] [[sample]] the lower the [[Count Rate|count rate]].
: For an [[Alpha Particle|alpha]] source the [[Count Rate|count rate]] drops to 0 beyond 5cm because the [[Alpha Particle|alpha particle]]s are [[Absorb (Physics)|absorbed]] by a few [[centimetre]]s of [[air]].
: For a [[Beta Particle|beta]] source the [[Count Rate|count rate]] drops to 0 beyond a few [[metre]]s because the [[beta Particle|beta particle]]s are [[Absorb (Physics)|absorbed]] by the several [[metre]]s of [[air]].
: For a [[gamma-ray]] source the [[Count Rate|count rate]] drops at a rate of 1/r<sup>2<sup> where r is the distance between the source and detector.