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In my textbooks, youtube videos, different websites, I have seen that during calculations regarding interference of waves we derive the equations in such a way as if there is no distribution of energy by waves., I mean if it is a circular wave then the diameter of locus wavefronts will increase witth the passage of time by indulging more and more particles and involving new particles has to be done by distributing energy(as far as I know). So shouldn't this cause change in amplitude as time passes? Moreover aren't each wavefronts subject to countless interferences causing it to distort largely from its initial form?

An intuitive approach will be much more helpful. Thank you.

MSKB
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1 Answers1

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Normally we use coherent lasers or collimated beams of coherent atoms in interferometers. The spreading of the waves in the transverse directions relative to the propagation is taken to be negligible over the extent of the wave propagation. Even if this isn't so, the phase of the wave is independent of the amplitude, the subsequent interference caused by a phase difference only diminishing in amplitude with any spreading of the wave over space.

It is not necessary to discuss the additional complexity of how the amplitude of a particular wave evolves to explain the cause of interference, a phase shift. This is probably the most likely reason why explanations of interference leave this out.

jamie1989
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  • https://physics.stackexchange.com/a/665502/288378 – MSKB Sep 12 '21 at 21:14
  • Please check out the above answer and if that answer is right, based on that how is linearity of waves maintained? – MSKB Sep 12 '21 at 21:15
  • Based on your answer I have one question that is lets say we took a paper and pushed a pen from below so a bump is formed by taking the particles adjacent to the point of action a bit upward. Shouldn't a wave act in that a way too? If we think of water wave as far as I can think intuitively, waves should spread largely and shouldn't this actually change amplitude largely which seems to be counterintuitive with your answer? – MSKB Sep 12 '21 at 21:19
  • Of course my knowledge about this stuff is 1 millionth of yours but looking forward to understand the fact – MSKB Sep 12 '21 at 21:20
  • @MSKB yes a water wave's amplitude will diminish as the wave propagates from a single origin. I'm not sure how that is counterintuitive with my answer? I discussed the specific case of interferometers, devices that use wave interference to measure effects. And the case where amplitudes do vary, mentioning that this doesn't need to be considered in a preliminary discussion of interference. – jamie1989 Sep 13 '21 at 06:57
  • I felt like that I am not sure anyways......I was just asking about the fact – MSKB Sep 13 '21 at 10:07