for 
corresponds to minima as discussed earlier. The second condition : 
gives the position of maxima.
Solution of transcendental equation can be determined graphically, where two functions 
and 
are plotted against 
(Fig.4). The point where these two curves intersects, satisfies 
and these values of 
corresponds to secondary maxima in the diffraction pattern. The corresponding values of 
.This clearly shows that the secondary maximas are not exactly midway between the two minimas but are slightly displaced towards the principle maxima. The intensity at the mid way between two minima is 
where n=1,2,3..... and is slightly less than the intensity at the secondary maxima. The intensity of the first secondary maxima is 
times the intensity of principal maxima.
The first minima in single slit diffraction pattern occurs for 
. The width of central maxima at a distance D from the slit is thus given by 
, where 
is the distance between the position of peak in central maxima and first minima.