Interference occurs when coherent wave sources emit waves that overlap and combine, resulting in a new wave.

Interference is a fundamental principle in wave physics. It takes place when two or more waves travel through the same medium and meet. Coherent wave sources are defined as those that emit waves with a constant phase difference. This means that the waves can be consistently in phase or out of phase, leading to two types of interference: constructive and destructive.

Constructive interference happens when the crest of one wave aligns with the crest of another wave, or when the trough of one wave coincides with the trough of another. In this case, the amplitude of the resultant wave is the sum of the amplitudes of the two interfering waves. This results in a wave that has greater intensity or brightness, particularly in the context of light waves.

Conversely, destructive interference occurs when the crest of one wave meets the trough of another. Here, the amplitude of the resultant wave is the difference between the amplitudes of the two interfering waves. This can lead to a wave of reduced intensity or even complete darkness, especially for light waves.

The formation of interference patterns from coherent wave sources is crucial for various scientific and technological applications. A notable example is the double-slit experiment, where light from a single source is divided into two coherent sources by passing it through two closely spaced slits. As the light waves from these slits overlap on a screen, they interfere to create a pattern of alternating bright and dark fringes. This experiment serves as compelling evidence for the wave nature of light.

In conclusion, interference arises from the overlapping and combining of waves emitted by coherent sources. The characteristics of the resultant wave, whether it exhibits increased or decreased amplitude, depend on the nature of the interference—constructive or destructive. This relationship is dictated by the phase difference between the interfering waves, which remains constant for coherent sources.