Diffraction occurs when a wave moves through an opening in a barrier. This causes the wave to change direction and spread out.
Waves can behave in three different ways depending on the obstacles they encounter. They can reflect, refract or diffract. In diffraction, waves such as sound, light or water either bend around small objects that obstruct their passage or spread out as they travel through a gap in the barrier.
The degree of diffraction forms a direct relationship with wavelength. It generally increases as wavelength increases. Conversely, the amount of bending lessens as wavelength decreases. However, if the opening of the barrier is smaller than the wavelength, the effect of diffraction is not easily observed. Hope this helps.