It also explains why sound can be heard around a corner even though no straight path exists from the source to the ear. Diffraction of light differs from diffraction of sound because diffraction is most evident when the obstacle is about the same size as the wavelength diffracted. The sound waves we hear have wavelengths of about a yard and are diffracted by ordinary objects. Thus, light waves can be diffracted noticeably only by extremely small objects. How diffraction occurs.
Diffraction takes place among all waves at all times.
To understand why it becomes noticeable only when the obstacle is about the size of the diffracted wavelength, one must understand both diffraction and interference. Christiaan Huygens, a Dutch scientist, developed the principle that explains why diffraction occurs. This principle states that each point on the surface of a wave is the source of small waves. These wavelets move outward in all directions. To find the total wave reaching an area, all the wavelets that strike the area must be considered.