How do you work out half-life in physics?

Hi Hassan, the half life determines how fast a radioactive material decays. For example if I had 1kg of Uranium, and it had a half life of 10 days, that means that after 10 days, half of the Uranium would have decayed and I'd only have 0.5kg of Uranium left that hadn't decayed. There are some formulae to calculate the half-life, and it would depend on the context. You can book a session by clicking on my profile if you'd like to go through it in more detail

Half life in Physics is the amount of time it takes for a radioactive sample to reduce it's mass by a half. Radioactive materials undergo something called "decay": The atoms of the material break down, releasing some energy and some mass in form of other particles being released. The half time is just the amount of time it takes for 50% of the original sample to decay and change into another material. So an example would be this: Take a 1 kilogram sample Cobalt 60. If you wait about 5 years, half of that sample will have decayed and changed into Nickel, so you'll end up with 0.5kg of Cobalt and 0.5kg of Nickel

Half-life has two possible definitions, either: 1) The amount of time taken for the unstable nuclei in a sample to half or 2) The amount of time for the activity of the sample to half If for A level, you would take the equation N=N_0*e^(-lambda*t) , substitute 1/2 N_0 in the place of N, then solve for t, which would end up being ln(2)/(lambda). If for GCSE, you wouldn't need to calculate it, but you would draw lines across on the graph given to find the time taken for the activity/ number of unstable nuclei to half.