I have a problem in understanding the diffraction phenomenon. At first, it is described in simple way
If a wave encounters a barrier that has an opening of dimensions similar to the wavelength, the part of the wave that passes through the opening will flare (spread) out —will diffract—into the region beyond the barrier. The flaring is consistent with the spreading of wavelets in the Huygens construction
And then, when it gets into detail in each case, in single slit analysis to find the minima:
At this point, I don't understand why those rays can meet at such point P. Because, as the 1st picture an Huygens' wavelets, at first those light rays are parallel and then after it goes past through a narrow opening, it flares, but does not come to on point as the direction of the 1st picture. To be more clear, how can those light rays that diffract/diverge converge at one point like the 2nd picture?