Standing Waves and nodes

  • Thread starter jsmith613
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  • #76
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Could you tell the difference by looking?
The con and des terms are only approximate, aren't they? Certainly only useful for arm waving or, sometimes, for finding a minimum / null in interferometry etc.. What is really relevant is the actual value.
If they are from non-coincident sources you would, in fact, be producing a two slits interference pattern.
surely in an ideal situation (such as an exam question - which is one of the things I am working towards) they may ask the basic question
"Wave A and B are 10 degrees out of phase. When they superimpose would we get a constructive or deconsrtuctive interferance pattern. Explain"

In this case would the following answer suffice
"They would interfere constuctivley as the total displacement is greater than that of both individual waves".



Maybe i was confusing myself by using the value 1 degree. It would actually ONLY make sense if deconstructive intferferene took place at 180 degrees out of phase, right?

Reason being that this is the only stage where maximum displacement is less than that of either / both waves individually?
 
  • #77
sophiecentaur
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Any decent Science exam question would really not concern itself with such semantic ideas. If it were to ask you what the value of the resultant was, you should be able to work it out with a simple vector triangle and get full marks. If you were at too low a level of knowledge then an appropriate question wouldn't introduce the phase value.
You seem determined to keep this topic at a 'conversational' level when, as I have remarked twice already, the Maths say it all and, at your level, that's what would count. It really is the only way forward. I have never come across any question on the lines of your proposed one - for a start, what could be the marking scheme?
All one can say, conversationally, is that the maximum is for zero phase difference and the deepest part of a null is when they are in antiphase - but we all knew that even before this thread started.
 
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