Re: [Phys-L] [SPAM] Re: A waves question

[Andre Adler <andre.adler@gmail.com>]

The subject is not a standing wave on a string, but there is a nice description in the January 2010 issue of the Physics Teacher by Chiu-king Ng (page 46) entitled Energy in a String Wave that might help understanding the standing wave on a string. 


On Jun 22, 2012, at 3:02 PM, Anthony Lapinski wrote:

> Well, for a standing wave (any wave) on a string, the string must be taut.
> No tension, no velocity, no frequency. So maybe the energy is
> stored/transferred due to the force in the string. Not sure how this
> applies to light waves or other EM waves.
>
> Phys-L@Phys-L.org writes:
> > But isn't that what he was asking... what happens to the energy at the
> > nodes... the rope is not moving to convert energy into movement, so where
> > is the energy?  
> >
> > On Jun 22, 2012, at 1:52 PM, Andre Adler wrote:
> >
> > > Destructive interference does not necessarily occur every the
> > individual waves are, but if it is a standing wave, such as on a rope,
> > the rope has kinetic energy of motion (except at the nodes).
> > > On Jun 22, 2012, at 1:33 PM, Peter Schoch wrote:
> > >
> > > > A fairly inquisitive student came up with the following question, and
> > I thought I'd get the reaction of the list as to the best answer.
> > > > The course is "Liberal Arts Physics" -- designed as a survey course
> > for those LA majors that need one semester of a science.  The theme was
> > energy conservation (a bit broad, and I would narrow it a bit next time I
> > do it).
> > > > We are discussing waves.  The student asked the following (more or
> > less)
> > > > If a wave can transit energy that is proportional to its amplitude
> > squared, and energy can't be created or destroyed, what happens to the
> > energy when two waves destructively interfere?
> > > > Peter Schoch
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