Radioactivity was first noticed by French physicist, Henri Becquerel, in 1896, when he observed that some photographic plates which had been stored close to a uranium compound had become partly exposed or ‘fogged’.
Gamma radiation can be significantly reduced by…
A sheet of paper
A 3 mm thickness of aluminium
Several cm of lead
Gamma radiation is...
An electromagnetic wave
A helium nucleus
Which form of radiation has the highest ionising power?
What causes an atom's nucleus to become unstable?
Too many or too few neutrons in the nucleus
More electrons than protons
Fewer electrons than protons
What is the activity of a source that emits 1,200 particles per minute?
Which type of radiation has the greatest range in air?
What is the atomic number Z ( ) of the nitrogen nucleus formed in the decay of carbon-14?
What is the half-life of a radioactive source?
Half the age of the source
The time taken for the activity of the source to fall to half the original activity
Half the time taken for the activity of the source to fall to zero
A radioactive source has an activity of 3600 Bq and a half-life of 14 days. What is the activity of the source 42 days later?
A radioactive sample has a count rate of 10,000 Bq. 24 days later the activity has fallen to 625 Bq. What is the half-life of the sample?