The fraction `f` of radioactive material that has decayed in time `t`, varies with time `t`. The correct variation id given by the curve.
.

Options

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

Answer

B

Explanation

(b) Number of atoms undecayed `N = N_0 e^(- lamda t)`
Number of atoms decayed `= N_0 - N = N_0 (1 - e^(- lamda t))`
rArr Decayed fraction `f = (N_0 - N)/(N_0) = 1-e^(-lamda t)`
i.e, fraction will rise up to `1`. Following exponential path as shown in graph (B).