9A.2 Rate Of Radioactive Decay Flashcards
what is decay constant
the probability, per second, that a give nucleus will decay
the decay of a nuclues is not dependent on
any external factors like temperature, pressure, other nuclei, its decay is complete independent
what is activity of a radioactive source
the number of radioactive decay in unit time
what is the formula for activity
A = - λ N (n = number of nuclei in a smaple) the negative sign is their since the number of nuclei is decreasing but we usually don’t include it in calculations also A = dN/dt
what is the formula for the number of nuclei of a radioactive sample after time t
N = No * e^- λt( we get this form the differential equation of dN/dt = - λN
the rate at which the activity decreases depends on
the particular isotope
what is half-life
the time taken for half the nuclei within a sample to decay, alternatively it is the time taken for the activity of a radioactive nucleoid to reduce to half its value
what is the formula to calculate half life
Ln2/ λ (derivation is page 138)
how can we measure radioactive decay rates
have a radioactive source across a G-M tube and measure the activity and then plot a graph of activity over time page 139 (safety)
what is the exponential decay equation of A
A =Ao*e^- λt since A is proportional to N
how can we find the half life using a activity against time graph
get a suitable starting activity after that divide it by 2 and find the time taken for the value to half and then after that keep halfling the value and get the time taken for it to half, from their get the average time and that will be the value of the half-life
why do we take multiple reading of the half life from a activity-time graph when determining the half life of a radioactive source
to constipate the randomness of decay and the graphical and experimental errors.
why do we convert the exponential decay equations into straight line equation
to lower the uncertainties when calculating the half life as our best fit line will be easier to graph
how can we convert our exponential decay equation into straight lines
just take logarithms of both and get the equation
what is the straight line equation for A=Ao*e^- λt
ln A= - λt + ln Ao with m= -λ
