The half-life period of a radioactive element X is the same as the mean life of another radioactive element Y. Initially, both of them have the same numbers of atoms then,
X and Y have the same decay rate initially
X and Y decay at the same rate always
Y will decay at a faster rate than X
X will decay at a faster rate than Y
C.
Y will decay at a faster rate than X
The half-life of x - mean life of y
Let λx and λy be decay constants of x and y, then condition (1) implies
As rate of decay αλ; hence decay of y will be faster than that of x.