T1/2=ln(2)λ≈0.693λcap T sub 1 / 2 end-sub equals the fraction with numerator l n 2 and denominator lambda end-fraction is approximately equal to the fraction with numerator 0.693 and denominator lambda end-fraction For general calculations of the remaining mass ( Ntcap N sub t ) after a certain time (
National 5 Physics | Radiation | Half-life | WORKED EXAMPLES
: Half-life is constant for a specific isotope and cannot be changed by physical or chemical means. Half-Life-Alyx-TRNT.rar
) of a radioactive isotope is the time required for half of the unstable nuclei in a sample to undergo radioactive decay. :
: Draw a horizontal line from this half-value to the curve, then a vertical line down to the time axis (x-axis). T1/2=ln(2)λ≈0
A common method for finding half-life is using a decay curve (activity vs. time). : Locate the starting point ( N0cap N sub 0 ) on the vertical axis (y-axis). Calculate Half-Value : Divide the initial activity by 2 (
: The distance from zero to that point on the time axis is one half-life. Examples of Isotopes A common method for finding half-life is using
Nt=N0(12)tT1/2cap N sub t equals cap N sub 0 open paren one-half close paren raised to the the fraction with numerator t and denominator cap T sub 1 / 2 end-sub end-fraction power Determining Half-Life from a Graph