The graph which represents the correct variation of logarithm of activity (log A) versus time, in figure is.
.

Options

A. A
B. B
C. C
D. D

Answer

D

Explanation

(d) Activity `A = lamda N_0 e^(-lamda t)`
`rArr log_e A = log_e lamda N_0 + log_e e^(-lamda t)`
`rArr log_e A = log_e C - lamda t (Take lamda N_0 = C)`
`rArr log_e A = -lamda t + log_e C`
This is the equation of a straight line having negative slope `(= -lamda)` and positive intercept in `log_e A` axis.