Question:Does diffraction cause any practical problems?
Yes, microscopes and telescopes are both optical systems.
If an optical system were made absolutely perfectly then the ultimate limit to its performance is determined by diffraction.
Because light must pass through a gap at the end of the optical instrument and this causes some diffraction.
This causes images of that object to blur because diffraction from one point on the object interferes with rays coming from neighbouring points on the object.
The diagram shows how diffraction affects a single point of light, imagine if every point on an object was replaced by these ring patterns - this is the cause of the blurring of images.
In order to see any object light must reflect from the object to our eyes; if the size of an object, or a feature on an object is close to the wavelength of light then we find the light reflecting from the object diffracts just as though travelling through a gap.