Diffraction is a phenomenon observed with all forms of waves, including, light, sound, and water. It involves the change in direction of waves as they pass around a barrier or through a small opening.
An example of this is a water wave traveling behind a stationary boat near the shore. Another example is the ringing appearance of light passing through a small hole in a sheet of paper as it is reflected off a wall. It happens because when waves are disturbed, they create new waves of varying wavelengths and amplitudes. The constructive and destructive addition of these new wavelengths of light produces the diffraction pattern.
New wavelenghts of light produces diffraction pattern.