ABSTRACT
The type of growth shown in Fig. 10.1 is termed exponential or logarithmic. The series 1, 2, 4, 8, 16, 32, etc. can be expressed as 20, 21, 22, 23, 24, 25…Therefore, if log2 N is plotted against time, the straight line relationship shown in Fig. 10.2 is obtained. This is a more convenient graphical representation of the data, since the gradient of the line gives the exponential growth rate, K:
If tables of logarithms to the base 2 are unavailable the data can be plotted in terms of log10 N: since log10 N=0.301 log2N, K is given by
Growth rate can also be expressed in terms of the mean doubling time, 1/K. In the example given in Fig. 10.2 the exponential growth rate is 0.67 h-1, and the mean doubling time is 1.5 h.
