What is the basic difference between interference and diffraction?

Interference is a phenomenon that occurs when two or more waves overlap and combine to form a new wave pattern. This happens under the condition that the waves have a constant phase difference and are coherent. The result is a pattern of constructive and destructive interference, leading to bright and dark fringes.

Diffraction, on the other hand, is the bending of waves around obstacles and the spreading out of waves when they pass through small openings. This phenomenon is noticeable when the size of the obstacle or opening is comparable to the wavelength of the wave. Diffraction results in a pattern of varying intensity that is different from interference patterns.

In summary, interference is about the overlapping of coherent waves, while diffraction involves the bending and spreading out of waves.