(i) A graph of the number of undecayed nuclei N of a radioactive sample against time approaches the time axis but never actually touches it. Explain the physical reason for this behaviour.
(ii) Describe a graphical method of obtaining the half-life of a radioisotope from its semi-log plot of lnN versus time without performing any algebraic calculation.
(iii) If log10N is plotted on the ordinate instead of lnN, how does the numerical value of the slope change? State the factor relating the two slopes.