Radioactivity and Particles: Half-Life

‘Half-life’ refers to the length of time it takes for half the atoms in a radioactive substance to decay.
It is impossible to predict when a particular atom will decay, but given a large number of atoms, predicting the average time for half of them to decay is possible. That’s the half-life.
Half-life is not affected by physical factors such as temperature, pressure or state of the substance. It is a characteristic property of the radioactive isotope.
Different isotopes have different half-lives, ranging from fractions of seconds to billions of years.
After one half-life, the amount of radioactive material left is halved. After two half-lives, a quarter remains. After three half-lives, an eighth remains, and so on.
Over time, a radioactive substance continues to decay and become less radioactive, but it never completely loses all its radioactivity.
Half-life is crucial for determining the age of artefacts and fossils. This is known as radioactive dating or radiometric dating.
It’s also important in managing radioactive waste, as some wastes remain hazardous for thousands of years.
Real world applications include medical treatments, where doctors must carefully control the doses of radioactive treatment given to a patient, and in nuclear power plants, where half-life data helps control the reactors and prevent nuclear accidents.
Half-life graphs can be plotted to visualise the decay of a radioactive substance. The horizontal axis traditionally represents time, and the vertical axis represents the number of undecayed atoms or the radioactivity.
Calculating half-life involves understanding the exponential decay equation N = N0 * e^(-λt), where N is the final amount of undecayed material, N0 is the initial amount, λ is the decay constant, and t is time.
Remember, completing practise problems involving half-life calculations will be beneficial in understanding the concept and preparing for exams.