The significant difference between Diffraction and Interference is that Interference is the phenomenon if two waves of the same type overlap to give an alternating spatial variation of large and small wave amplitude. On the other hand, Diffraction is the phenomenon of whether a wave passes through an aperture or goes around an object.
In this article, you will explore the difference between diffraction and interference in detail with different examples and diagrams.
Diffraction Vs. Interference – Overview
The crucial difference between diffraction and interference is that when two separate wavefronts originating from two coherent sources produce interference. Secondary wavelets originating from different parts of the same wavefront are known as diffraction. Although, diffraction and interference are entirely different in nature. The region of minimum intensity is perfectly dark in interference. In diffraction, they are not perfectly dark.
We know that visible light is the type of electromagnetic wave to which our eyes respond. As we have seen previously, light obeys the equation
What is interference?
the term interference is used to characterize the superposition of a few coherent waves. In a young double-slits experiment, the interference fringes are all of the equal widths. in double-slit interference. bright fringes are of equal intensity. It causes the medium to take a particular shape.
The shape produces by interference is due to the whole or the net effect of two individual waves on the medium’s particles. Interference is the spreading of waves behind obstacles and the waves stay away from the original route in the same elastic environment. Interference occurs in a way that the superposition of waves starts from varying wavefronts.
It means there is a phase difference between the two waves or they are not coherent waves. when two components are of the same frequency and phase (i.e they vibrate at the same rate and are maximum at the same time) the wave amplitudes are reinforced forming constructive interference. All bright fringes in an interference pattern have the same intensity.
What are the conditions for interference?
- The light source should be monochromatic.
- The light source should be coherent mean they should not be independent but should be a subsidiary source and derived from a single source.
- The light source should be narrow and have the same intensity.
- For constructive interference path difference between light, rays should be an odd integral multiple of the wavelength of light.
path difference =0,λ ,2λ, 3λ,———–mλ
Where m=0,1,2,3,………
- For destructive interference, the path difference between the light rays should be an odd integral multiple of half the wavelength of light.
Path difference = λ/2 ,3λ/2 ,5λ/2 ,7λ/2 ,…………… (m+ 1 λ/2)
Where m= 0,1,2,3,…..
Interference examples in real life
- If two stones are dropped into a pool of water, waves spread out from each source, and interference occurs where they overlap
- Two wave trains of light from a double-slit produce interference.
What is Diffraction?
the term diffraction is used to characterize the superposition of large waves coming from different parts of the same wavefront. in a single slit diffraction pattern, only the non-central maxima are equal width which is half of that of the central, and it happens due to the spreading out of waves passing through an aperture. Aperture refers to the opening of a lens’s diaphragm through which light passes.
In the case of diffraction, the size of the aperture is of similar straight dimensions to the incident wave’s wavelength, and its occurrence is significant. Furthermore, it takes place if the traveling wavelength’s part gets obscured or shaded.
Read Also: Superposition of wave
Diffraction Examples
- The closely spaced tracks on a CD or DVD act as a diffraction grating
- The hologram on a credit card
- Optical Atmospheric diffraction
- The scattering of radio frequency of radio waves.
- Ocean waves diffract around jetties and other obstacles
- Sound waves can diffract around objects
Difference between diffraction and interference in tabular form
|
Diffraction |
Interference |
| Secondary wavelets originating from different parts of the same wavefront produce diffraction. | If two waves emerging from two different sources produce different wavefronts is known as interference |
| Diffraction occurs because of the superposition of secondary wavelets due to different points/parts of a wavefront. | It happens because of the superposition or overlapping of two waveforms that originate from two different coherent sources. |
| Varying fringes width that produces in diffraction. | Constant fringes width. |
| When diffraction occurs, the intensity falls quickly. In diffraction patterns, the intensity of successive fringes goes on decreasing. | Generally, bright fringes have the same intensity. |
| The fringes are wide near the obstacle. Fringes width goes on decreasing when approaching the shadow side. | Interference produces an intensity of all the points on maxima is of similar intensity. |
| The maxima may be of varying magnitude. | The number of maxima has the same magnitude of intensity. |
| In this pattern, the intensity of minima will be never zero. There will be poor contrast between dark and bright fringes. | The intensity will be very small or close to zero at minima which means minima produce dark fringe. There is a good contrast b/w the bright and dark fringe. |
Thus, this is the major difference between diffraction and interference. To know the differences between other topics in physics, chemistry, maths, or biology, you can search here for interesting content.
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