The diffraction happens when the light waves or waves of sound meet an obstacle and the phenomenon of diffraction is described as a change of direction of the straight path travelled by the waves.
The phenomenon of diffraction can be better observed if the size of obstacle is near or equal to the wavelength, hence, the larger the wavelength is, the sharper the bending diffraction angle is.
As reflection and refraction, diffraction is also a phenomenon that is explained as a change of direction of waves and all types of waves experience this phenomenon. For instance, due to the phenomenon of diffraction, the soundwaves can bend around corners, making possible to hear what happens in the room, next to our room.
The term diffraction is applied to problems in which one is concerned with the resultant effect produced by a limited portion of a wave surface. If only a part of the wave is cut off by some obstacle, are the effects commonly called diffraction. Diffraction is sometimes defined as the bending of light around the obstacle and its presence in the region of geometrical shadow.