Compare the fraunhofer diffraction patterns of single slit and double slit

In the single-slit pattern, most of the intensity is contained in a region just where you would expect it to be by tracing the path of a straight light beam from the source through the slit to the detector. However, due to the wave nature of light and the finite width of the slit, there is diffraction, giving rise to faint side lobes on both sides of the main central lobe.

In the double-slit pattern, the pattern has a similar shape, but it is divided into many smaller interference fringes due to constructive and destructive interference between the waves passing through one slit and those passing through the other.