In fact, the diffraction and interference of light are essentially the same thing, both of which are the coherent superposition of several coherent rays. However, interference is a coherent superposition of finite rays, which can be directly added algebraically. Diffraction is the superposition of infinite rays and must be calculated by integration.

180 1 year, British physicist Thomas Young (1773-1829) successfully observed the phenomenon of light interference in the laboratory. When two or more light waves meet in space, they are superimposed on each other, always strengthened in some areas, and always weakened in other areas, forming a stable distribution of strength and weakness.

In the process of light propagation, when encountering obstacles or small holes, light will deviate from the straight propagation path, and the phenomenon of bypassing obstacles is called light diffraction. The diffraction of light, like the interference of light, proves that light fluctuates.