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Optics interference basic

  1. Oct 16, 2009 #1
    why do we see 2waves when we consider interference ????why not three or four????eg when we find out conditions formaxima we look for condition when 2 waves interefere...why not 3????
  2. jcsd
  3. Oct 16, 2009 #2


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    Staff: Mentor

    It's certainly possible to consider more than two waves interfering. In my optics course I cover examples such as multiple-slit interference. And any diffraction situation (e.g. single-slit diffraction) is basically an infinite number of waves superposing together, which you analyze by integration rather than by simple addition.
  4. Oct 16, 2009 #3
    what i meant is that we calculate the condition for maxima by taking 2 waves interefering but if we do by 3 waves then surely answer will be different...so why do we do by taking 2 waves
  5. Oct 16, 2009 #4


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    It depends on the situation. If there are 2 waves present, we calculate using 2 waves. If 3 waves are present, we must use all 3 waves.

    If you are referring to physics homework problems, we use 2 waves because that is easier to calculate and we want you to learn the basic principle by doing simpler calculations.
  6. Oct 17, 2009 #5
    sorry i couldnt get you people to make it simple i was saying that we find net intensity at a point by finding net intensity between 2 waves why not threee why are we breaking waves in pairs why not in 3 waves in a group?
  7. Oct 17, 2009 #6
    Hello prashantgolu,I think you are confusing "two waves" with "two sources".In the simplest analysis of the Youngs fringe experiment we might,for example,consider just two waves only,one from each source, to find the position of the maxima caused by these two waves.There is,however, a whole group of waves from each source and a more detailed analysis which accounts for the intensity variation across the maxima and minima would consider these whole group of waves.If there were three sources there would be three groups of waves and so on.
  8. Oct 19, 2009 #7
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