Utilisateur
- Their size
- They have too many neutrons
- They have too little neutrons
The process of emitting radiation (A random process)
- There's an equal probabitily of any nucleus decaying
- The rate of decay is unaffected bythe surrounding conditions
- You can only estimate the proportion of nuclei decaying in a given period of time
A Geiger-Muller Tube
Provides evidence that radioactive decay is a random process
A = λN
A = Activity
λ = Decay constant
N = Number of Unstable nuclei
The probability that a nucleus will decay
The rate of decay of a radioactive source
A = A0e^-λt
N = N0e^-λt
λt1/2 = ln(2)
- The ratio of carbon-12 to carbon-14 is constant in all living things
- Once a living orgainsm dies, it stops absorbing carbon and the carbon-14 continues to decay
- The ratio of carbon-12 to carbon-14 is measured in a dead and living sample
5700 years
In the atmosphere, via cosmic rays
Carbon-14 can also sometimes decay back into Carbon-12 via beta decay.
We assume the ratio between carbon 14 and carbon 12 is constant, however we don't take into account other factors e.g. fossil fuels
It cannot be used to date extremely old objects as it has a half life of 5700 years which isn't long enough
- Measure the background countrate with the geiger muller tube & counter (1 min)
- Repeat 3 times to get an average
*Wear gloves and use tongs to handle radioactive sources.
*Don't stand in front of the sources
- Place the radioactive source at a fixed distance in front of the GM tube and measure the countrate (1 min)
- Subtract the background countrate from the countrate of the radioactive source to get the real countrate
- Place your test material between the tube and radioactive source and measure the countrate (if it stops then that material stops that radiation)