Diffraction of water waves (opening)
|A wave spreads out (noticeable diffraction) when the size of the slit is comparable to or smaller than the wavelength.|
When waves reach a narrow slit, the water in the slit vibrates like a point source. The waves thus sent out from secondary sources along the slit are nearly in-phase when arriving any point in the forward direction. The diffracted wave resembles a circular wave with centre at the slit.
|A wave goes straight when the size of the slit is much larger than the wavelebgth.|