Physics G Radioactivity - Halflife Flashcards
An isotope has a half-life of 3 days. How long would it take for a sample of the isotope to decay to one eighth of the original value?
9 days
A sample of an isotope has a count rate of 200. Forty days later the count rate has dropped to 25. Calculate the half-life of the isotope.
13.33 days
If an isotope has a half-life of 20 seconds then how long will it take for its activity to drop from 1000 to 125?
60 seconds
Explain what is meant by the term half-life.
The amount of time it takes for half of the atoms in a radioactive substance to decay.
Explain what is meant by unstable nuclei.
It could decay at any time.
The activity of a radioactive source is the number of ioninsing particles it emits per second. This is measured in what?
Becquerels Bq
Carbon-14 has a half-life of 5700 years.A sample of cloth contains 6.0 g of carbon-14.What mass of carbon-14 will remain in the cloth after 11 400 years?
1.5g
Why are some isotopes described as stable?
Stable isotopes do not emit ionising radiation.
