(51)
Substituting for 
from equation
(51) in equation (50),
Now,
Consequently,
the term 
and those
higher can be
ignored with respect to 
.
Then,
and
(52)
Equation (52) shows that the points of inflection occur at 0.6065 of the peak height. It follows that the peak width, at 0.6065 of the peak height, will be equivalent to two standard deviations (2s) of the Poisson or Gaussian curve.
