Difference Between Diffraction and Interference

Diffraction and interference both quantities that come in the study for mechanics. In everyday usage the two terms may have similar connotations, however, in electronic science, the two terms have two separate meanings. Here this article gives the main key difference between them to better understand this topic.


Definition of Diffraction:

Diffraction is the phenomenon of spreading of the light wave when it passes through a slit or any small gap.

Definition of Interference:

Interference is the act of superposition of two or more light waves emitted two coherent sources traveling in the same medium. We know the coherent sources provide a light wave of the same frequency and constant phase difference.


The main key difference between diffraction and interference:

  • Diffraction. there is a variance of the intensity of positions, In interference, the intensity of all the positions on maxima are of similar intensity in interference.
  • In Diffraction, the width of the fringes is not equal in interference, While the interference the width of fringes in interference is equal to the interference.
  • In the case of diffraction, there is a variance in the intensity of interference, It is absolutely dark in the region of minimum intensity in case of interference.
  • Diffraction can be termed as the secondary waves that emerge from the different part of the same wave, Interference may be defined as waves emerging from two different sources producing different wavefronts.
  • For diffraction to take place slit or obstacle is necessarily required but for the wave interference there exists no such requirement.
  • If the number of sources is many, that is more than two then it is referred to as diffraction sources, If the number of sources is few such as two sourced, then they are referred to as interference sources. 
  •  The diffraction process is poor contrast between maxima and minima while interference exhibits good contrast between maxima and minima.
  • The direction of propagation of wave gets changed, whereas in case of interference the superposed wave travels in the same direction.
  • Diffraction is the result of light propagation from distinct parts of the same wavefront, while interference is the result of the interaction of light coming from two separate wavefronts.
  • The minimum intensity points in the case of diffraction are not completely dark, as against in case of interference the point of minimum intensity shows complete darkness.
  • In diffraction superposition of waves spreading in the same material environment, while interference waves stray from the original route in the same elastic environment.
  • In direction between different fringes is nonuniform in diffraction, while in the case of interference the spacing between the fringes exhibits uniform nature.
  • Diffraction there is a constant phase difference between the waves, while in interference the dimension of the cracks should be the same size as the wavelength.

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