Thus, when a wave comes against a barrier with a small opening, all but one of the effective point sources are blocked, and the light coming through the opening behaves as a single point source, so that the light emerges in all directions, instead of just passing straight through the slit.
Diffraction limits the resolving power of microscopes and other magnifying devices.
If the object being viewed is smaller than the wavelength of light used, then the light diffracts around the object, and severely distorts the image.