decay

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Unstable atoms are radioactive.

Radioactivity can be modelled by exponential decay

The number of atoms that decay per second is the activity

Activity is proportional to size of sample

activity = decay constant x number of atoms

A = λ N

rate of decay = -activity

dN/dt = -λN

half-life = time taken for numbers to half

T(1/2) = ln2/λ

number of atoms remaining = original number of atoms x e^-λt

N=N0 x e^-λt

use the log graph to find decay constant;

if the log graph is straight, it is exponential decay!

ln(N) = -λt + ln(N0)

y = mx + c