Is the cast itself a transverse wave?

[Graeme H]

I don't know if you're seeing it from the wrong perspective or not Lasse.

That quoted post was in response to the one from James. His post stated that a loop is not wavey enough because it doesn't have amplitude, wavelength or frequency. I'm saying that's only because the medium is not long enough for them to be measured; increase the length of the medium and those aspects could be measured.

Cheers,
Graeme

[Merlin]

The transverse waves that can be seen are either those produced by a dip in the tip trajectory (tail), which travel along the fly leg down to the leader, changing amplitude (at least) because of the change in mass per unit of length of the line/leader; and those produced by tip wobbling which travel along the rod leg in the direction of the loop.

The "wavey" loop is not a transverse one, I don't know if there is a name for that (would it be of a longitudinal kind?). I have the same questionning than Lasse, I cannot see why adding a long piece of string would change the wavy nature of the loop. You can describe loop propagation speed with usual wave characteristics (tension, linear density of the line), I have to look deeper to see if an amplitude can be defined (e.g. the "radius" of the loop), and frequency/wavelength; all that is not obvious to me.

Merlin

[Lasse Karlsson]

Hi Graeme

I don't know either

But aren't you saying that we just need to extend the line to be able to measure? That doesn't sound right..

Cheers
Lasse

[Graeme H]

Maybe this video I just put together will help. Or maybe not ...



Still, my question remains: isn't a cast just one of these rod oscillations extended greatly and not pulled back to keep the waves going?

Cheers,
Graeme

(The Feline Anti-Tangle Device refers to an earlier video of mine where my cat (pictured on the left) was playing with my leaders in this video.)

[gordonjudd]

frequency/wavelength; all that is not obvious to me.

Merlin,
I don't see how you can get a frequency or a wavelength value on the transverse wave that is generated with a one time mend either, but I would still consider them to be a transverse wave propagating down a medium.

Maybe we can agree with the statement in the Wikipedia article on waves that

A single, all-encompassing definition for the term wave is not straightforward. A vibration can be defined as a back-and-forth motion around a reference value. However, a vibration is not necessarily a wave. An attempt to define the necessary and sufficient characteristics that qualify a phenomenon as a wave results in a blurred line.

Graeme's video is a good example of the blurring of the line where the transverse waves in the first part of the video transition to become a "fly wave" at the end.

Gordy

[VGB]

Merlin,
I don't see how you can get a frequency or a wavelength value on the transverse wave that is generated with a one time mend either, but I would still consider them to be a transverse wave propagating down a medium.

Gordy

I can't see how you can have a transverse wave without a wavelength.

regards

Vince

[gordonjudd]

I can't see how you can have a transverse wave without a wavelength.

Vince,
Maybe we are getting too hung up on definitions, but to me a transverse wave is:

For transverse waves the displacement of the medium is perpendicular to the direction of propagation of the wave. A ripple on a pond and a wave on a string are easily visualized transverse waves..

Thus I think a the wave produced by a mend would qualify as transverse wave, since the displacement of the line/medium is perpendicular to the the direction of the propagation of the mend going down the line.

However, if you consider that the wavelength is

Wavelength, distance between corresponding points of two consecutive waves. ..

Then, I don't see that a transverse wave produced by a one-time sideways movement of the tip has a frequency (or a wavelength for that matter) since there is no second wave.

Gordy

[VGB]

Gordy

If you read down your wiki link, you will see some further definition:

Consider a traveling transverse wave (which may be a pulse) on a string (the medium)

On a wave pulse, frequency is measured at the rate a wave pulse passes a point.

Vince

[Graeme H]

I can't see how you can have a transverse wave without a wavelength.

Vince,
Maybe we are getting too hung up on definitions, but to me a transverse wave is:

For transverse waves the displacement of the medium is perpendicular to the direction of propagation of the wave. A ripple on a pond and a wave on a string are easily visualized transverse waves..

Thus I think a the wave produced by a mend would qualify as transverse wave, since the displacement of the line/medium is perpendicular to the the direction of the propagation of the mend going down the line.

However, if you consider that the wavelength is

Wavelength, distance between corresponding points of two consecutive waves. ..

Then, I don't see that a transverse wave produced by a one-time sideways movement of the tip has a frequency (or a wavelength for that matter) since there is no second wave.

Gordy

In my video, the direction of propagation of the wave is vertically down, the amplitude is measured horizontally and the wavelength is measured vertically.

When the amplitude of the wave becomes very much greater than the wavelength we get a recognisable loop. When we also limit the length of the medium (the fly line) we get a single wave that "breaks" and is also known as a cast.

If I had shot the video with only 2m of line outside the tip, we'd have a series of very fast casts. With the 50' of line I was using, the casts do not consume the whole line, so it shows several waves. That continues until I increase the amplitude of the waves beyond a threshold. When that threshold is reached, the wave becomes a cast and what we refer to as a loop is the only remaining portion of the wave.

There is no second wave because the wave has reached the end of the medium and the energy has been expended.

A mend is another transverse wave of higher frequency and MUCH lower amplitude than the cast and in another orientation to the propagation direction of the cast wave (vertical).

Cheers,
Graeme

[Graeme H]

Follow up diagram to the post above:

waves.jpg (59.58 KiB) Viewed 3379 times