Why longer wave diffracts more?

[kelvin490]

We have learned that for the same aperture, waves with longer wavelength diffract more than shorter waves when passing through the aperture. I would like to ask is this merely an experimental fact? Are there more fundamental principles behind this phenomenon?

 

[Dadface]

The diffraction pattern is in fact an interference pattern and can be found by summing the contributions of the waves from all of the imaginary point sources on the wavefront incident on the aperture.If the wavelength is made longer(or the aperture smaller)then for a given path difference and order of interference, the waves diffract through a greater angle.Try googling for details.