Article by:Ouma George,Awel Eshetu and Bassein Natalia
Coherence and Interference
Ø Introduction
Coherence and Interference are two ideal wave features that complement each other.The wave interference do occur but for it to be considered constructive interference,it needs the coherence of some of the physical quantities of the waves involved; the wavelength, amplitude, and phase of the constituent wave forms must be identical.The most distinct concept of coherence in waves requires that the wave are in phase,their peaks are aligned with each other.
Ø Coherence
This is a property holding for two or more waves with logical and consistent ability of sticking together, it is a wave feature marked with an orderly correlation between waves having identical physical quantities."Coherence describes all properties of the correlation between physical quantities of a single wave, or between several waves or wave packets"[1].This physical phenomena can be observed in practical lab experiment carried out to study characteristics of wave properties, the concept of wave coherence can be clearly visible when individual waves exhibit a constructive interference; a state at which the waves sum up and produce a compound sinusoidal wave form with an amplified crest as shown in Pic 1.The wave in blue color is the resultant wave of the two lime waves.
Pic1.Constructive interfernce.Modefied screen shot from an online source [2].
While constructive interference amplifies the output signal, the destructive interference does the opposite hence causing the input signals to cancel each other and a result weakens the output or destroy it producing a non-aligned wave form ,Pic 2.
Pic2. Destructive interfernce.Modefied screen shot from an online source [2].