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``Interference'' is the more general concept: it refers to the phenemenon of waves interacting. Waves will add constructively or destructively according to their phase difference. ``Diffraction'' usually refers to the spreading wave pattern from a finite-width aperture.
Two separate wave fronts originating from two coherent sources produce interference. Secondary wavelets originating from different parts of the same wave front constitute diffraction.The region of minimum intensity is perfectly dark in interference. In diffraction they are not perfectly dark.Width of the fringes is equal in interference. In diffraction they are never equal.The intensity of all positions of maxima are of the same intensity in interference. In diffraction they do vary.When we have two infinitely narrow slits separated by a distance apart near the source, we get interference. But when we have a single slit of finite width or rather an aperture near the source, we get diffraction.
The name interference itself gives it away. Two waves interfere or meet each other. When they do they cause an energy distribution which makes the famous bright and dark bands.Diffraction refers to the fact that waves can bend around things. Diffraction of sound is so common, that you must have never thought about it. But since light is a wave, it diffracts too.If you look at the two definitions, it would make one wonder, what’s the meaning of this question. The two phenomenon are so different and so nicely defined, why is there a confusion? Forget differences, what is even the similarity between the two?Well the confusion is caused by a lot of teachers and books. It’s because of captions given to the images like theseSome are called as interference patterns, and some others are called as diffraction patterns. Which is absolutely non sense. So here is what is really going on.In each picture, the light is made to pass through slit/s. When they do, the small opening makes the light diffract (bend around and spread out). So there is diffraction happening in all of these pictures. These waves, eventually meet each other and redistribute their energies, ergo, interfere with each other, which we can see as alternate dark and bright regions.So all patterns (bright and dark regions) are caused by interference of light (by the very definition of it), and in all experiments when slits are used there is diffraction happening at each slit.So it’s wrong to call something as interference or diffraction pattern. All are interference pattern itself.Then we have something called the diffraction grating. It’s called so, because it has lots of slits, and so light undergoes lots of diffraction, but again, eventually the pattern is caused by interference of light.Here is a CD. If someone asks what causes the colouration? If you say diffraction that’s wrong. The pits in the CD act like slits. So in that sense, its called a diffraction grating. But the coloration are caused by interference itself. Where you see Blue, it’s because the blue light is undergoing strong construction and rest, not so much. It’s not so different than the thin film interference, you see in oil spills and soap bubblesSo to summarise, all the energy distribution business, which causes coloration (in white light) or alternate dark and bright bands (in mono chromatic light) are called interference. Whenever waves spread out, or bend around a corner, it’s called diffraction. The two are worlds apart.
Two separate wave fronts originating from two coherent sources produce interference. Secondary wavelets originating from different parts of the same wave front constitute diffraction. Thus the two are entirely different in nature.The region of minimum intensity is perfectly dark in interference. In diffraction they are not perfectly dark.Width of the fringes is equal in interference. In diffraction they are never equal.The intensity of all positions of maxima are of the same intensity in interference. In diffraction they do vary.
Feynman has come from heaven to answer your question! Listen to him:No one has ever been able to define the difference between interference and diffraction satisfactorily. It is just a quest of usage, and there is no specific, important physical difference between them. The best we can do is, roughly speaking, is to say that when there are only a few sources, say two interference sources, then the result is usually called interference, but if there is a large number of them, it seems that the word diffraction is more often used.1To be more explicit read this passage from Ajoy Ghatak:We should point out that there is not much of a difference between the phenomenon of interference and diffraction, indeed, interference corresponds to the situation when we consider the superposition of waves coming out from a number of point sources and diffraction corresponds to the situation when we consider waves coming out from an area sources like a circular or rectangular aperture or even a large number of rectangular apertures (like the diffraction grating). 2Credits: 1 Feynman Lectures on Physics 2Optics-Ajoy Ghatak.
The first definition you give is correct:“Interference'' is the more general concept: it refers to the phenemenon of waves interacting. Waves will add constructively or destructively according to their phase difference. ``Diffraction'' usually refers to the spreading wave pattern from a finite-width aperture.” although I would add that diffraction also occurs at a sharp edge.The confusion occurs because some of the definitions are referring to diffraction patterns, which are interference patterns from a diffracted wave.You might like to read this http://www.math.ubc.ca/~cass/courses/m309-03a/m309-projects/krzak/
Correct. Diffraction = bending, interference = superposition. The confusion arises when you model diffraction by the superposition of wavelets, which always struck me as an unnecessary complication.
I don't think that diffraction is a subset of interference. We can produce diffraction without interference pattern.
a line on the surface of something along which it has split without breaking apart."a hairline crack down the middle of the glass"
The principle is almost correct, although the edge doesn't have to be sharp.
The name interference itself gives it away. Two waves interfere or meet each other. When they do they cause an energy distribution which makes the famous bright and dark bands.
Definition of diffraction: a modification which light undergoes especially in passing by the edges of opaque bodies or through narrow openings and in which the rays appear to be deflected
In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wave-front as a collection of individual spherical wavelets.[3] The characteristic banding pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image. This is due to the addition, or interference, of different points on the wave-front (or, equivalently, each wavelet) that travel by paths of different lengths to the registering surface. However, if there are multiple, closely spaced openings, a complex pattern of varying intensity can result.
The solution provided by the integral theorem for a monochromatic source is:where U is the complex amplitude of the disturbance at the surface, k is the wavenumber, and s is the distance from P to the surface.The assumptions made are:U and ∂U/∂n are discontinuous at the boundaries of the aperture,the distance to the point source and the dimension of opening S are much greater than λ.
Tipper Rumpf, PhD Optics, University of Central Florida (2006)Answered April 7, 2018Interference and diffraction are really the same phenomenon so the question is a little strange. They have slightly different connotations. Diffraction usually describes the spreading or splitting of a wave. Interference describes when there are two or move waves passing through the same location and the waves add or subtract (i.e. constructive or destructive interference).Perhaps an answer to your question is that diffraction produces waves at different angles and when these overlap you get interference.
Bill Otto, studied Physics & Chemistry at The University of Alabama in Huntsville (1976)Answered April 13, 2018Diffraction and interference are the same phenomena, and there is no clear distinction.Interference is usually used to characterize the effects of a very small number of slits or beams, while diffraction is used to characterize a large number of slits (such as a grating) or a large area such as the diffraction from from a telescope mirror.That said, there is no clear distinction between the two, and a discussion of why one is present with the other is moot, unless perhaps in your textbook the terms have been defined differently from the usual definitions.From The Feyman Lectures[1]the name has been changed from Interference to Diffraction. No one has ever been able to define the difference between interference and diffraction satisfactorily. It is just a question of usage, and there is no specific, important physical difference between them. The best we can do, roughly speaking, is to say that when there are only a few sources, say two, interfering, then the result is usually called interference, but if there is a large number of them, it seems that the word diffraction is more often used. So, we shall not worry about whether it is interference or diffraction, but continue directly from where we left off in the middle of the subject in the last chapter.
Jess H. Brewer, Physics professor since 1977.Answered May 11, 2018They are pretty much the same thing. The way we calculate single-slit diffraction is by breaking the slit up into an infinite number of infinitely small slits right next to each other and calculating the resultant interference pattern.468 viewsView Upvoters · Answer requested by Bashir Ahme
Vaibhav Sharma, Physics PhD Student at Cornell UniversityAnswered February 3, 2014Originally Answered: what is the diffrence between interference and diffraction ?In reality, there is no difference. According to Huygen's principle, each point is a source of a secondary wavelet. In both the phenomena, secondary wavelets interact and build up a pattern of bright and dark fringes. In interference, we consider the case where there are 2 or multiple slits and where the size or the aperture of the slit is ignored and only the distance between the two slits is taken into account. In diffraction, there is only one slit and thus it's size or aperture is taken into account.For interference, we consider mainly the interaction among wavelets coming from the two different slits by ignoring the size of the slit and assuming that only one wavelet is emitted from each slit. For diffraction, we consider the interaction among the different wavelets coming from the different portions of the same slit by accepting the fact that the slit is not just a point source but it has a finite aperture with many points. In reality, both diffraction and interference take place simultaneously.