[alancalverd]

Wave propagation in a string depends on whether you waggle one end of a long, soft, heavy rope, so you propagate sine waves along its length, or pluck the middle of a short, stiff, light wire whose ends are fixed, so you can only produce standing waves with nodes at the ends.

Apparently AI doesn't  know what a guitar is, or the difference between pluck and shake. Not that it matters at all, because anyone who wants to play a guitar knows exactly what they mean, and anyone who understands physics can spot bullshit. As usual, the contribution of AI is negative.

[hamdani yusuf (OP)]

Wave propagation in a string depends on whether you waggle one end of a long, soft, heavy rope, so you propagate sine waves along its length, or pluck the middle of a short, stiff, light wire whose ends are fixed, so you can only produce standing waves with nodes at the ends.

If the string is long enough, the wave doesn't have to be a standing wave.

[alancalverd]

It does on a guitar, because the ends are fixed. You might somehow induce a travelling or compression wave with a magnetic excitation of a steel string but the resulting frequency (MHz) will be far too high to contribute to the "wide rich sound...."

[hamdani yusuf (OP)]

(a) One end of a string is fixed so that it cannot move. A wave propagating on the string, encountering this fixed boundary condition, is reflected 180^o(π rad) out of phase with respect to the incident wave.

(b) One end of a string is tied to a solid ring of negligible mass on a frictionless lab pole, where the ring is free to move. A wave propagating on the string, encountering this free boundary condition, is reflected in phase 0^o(0 rad)  with respect to the wave.

I mentioned these merely to show a counter example of Bard's claim that all waves experience diffraction.

[alancalverd]

What has reflection to do with diffraction?

[Bored chemist]

It does on a guitar, because the ends are fixed. You might somehow induce a travelling or compression wave with a magnetic excitation of a steel string but the resulting frequency (MHz) will be far too high to contribute to the "wide rich sound...."

I'd like to see the maths on that. Take the average guitar string as having a length of 1 metre and the speed of sound in steel to be 5km/sec

[Bored chemist]

I mentioned these merely to show a counter example of Bard's claim that all waves experience diffraction.

The pictures do not show waves.

[hamdani yusuf (OP)]

What has reflection to do with diffraction?

It does on a guitar, because the ends are fixed.

[hamdani yusuf (OP)]

I mentioned these merely to show a counter example of Bard's claim that all waves experience diffraction.

The pictures do not show waves.

What do you think they show?

[Bored chemist]

I mentioned these merely to show a counter example of Bard's claim that all waves experience diffraction.

The pictures do not show waves.

What do you think they show?

Pulses.

[alancalverd]

It does on a guitar, because the ends are fixed. You might somehow induce a travelling or compression wave with a magnetic excitation of a steel string but the resulting frequency (MHz) will be far too high to contribute to the "wide rich sound...."

I'd like to see the maths on that. Take the average guitar string as having a length of 1 metre and the speed of sound in steel to be 5km/sec

So the lowest frequency that might propagate as a reflected longitudinal wave is 15 times the fundamental of the highest-pitched open string - that's not "rich" but "squeaky", and the harmonics are mostly beyond human auditory range.

Longitudinal standing compression waves are generated in wind instruments, not stringed ones.

[hamdani yusuf (OP)]

Longitudinal standing compression waves are generated in wind instruments, not stringed ones.

It can also be generated in a slinky.

[hamdani yusuf (OP)]

Pulses.

How many oscillations are needed to produce a wave?

[alancalverd]

One. The difference is that an oscillation has both positive and negative excursions about the equilibrium, whereas a pulse is a unidirectional displacement followed by a return to equilibrium.

[hamdani yusuf (OP)]

One. The difference is that an oscillation has both positive and negative excursions about the equilibrium, whereas a pulse is a unidirectional displacement followed by a return to equilibrium.

If there are more than 1 oscillations, would it make any difference?

[alancalverd]

No.

[hamdani yusuf (OP)]

No.

It means that a string or a slinky can produce traveling wave which doesn't diffract.

[alancalverd]

It can't diffract because it is constrained to travel along the length of the string. If you "bend" the string around a rigid fixture, the wave may reflect from the fixture but won't go around it, but if you bend the string with a flexible post, the attenuated wave will travel beyond the post.

So what?   

[hamdani yusuf (OP)]

if you bend the string with a flexible post, the attenuated wave will travel beyond the post.

Will you call it diffraction?

[alancalverd]

To the same extent that any other wave is diffracted by an obstacle.