wrote in message
...
On Wed, 16 Jan 2008 06:49:50 -0500, "Jim"
wrote:


wrote in message
. ..
On Tue, 15 Jan 2008 17:07:42 -0800 (PST), wrote:

On Jan 15, 7:50 pm, Tim wrote:
OK, I picked this up on another board,a nd seeing that Eisboch, Tom,
Gene and Larry have had dealings with this stuff. I thought I'd
present it here. It has my curiosity up as well.

I'm not up on physics, concerning this so here goes:

"I searched the web but couldn't find an answer to a simple question
which for my purposes is really a matter of curiosity. Of course,
sometimes these
kinds of questions end up teaching me the most.

Most defintions of wavelength are along the lines of the distance
between points of corresponding phase of two consecutive cycles of a
wave. I'm not
an idiot , so I understand what is a pretty
straightforward definition.

What I don't get is why the term length? I mean, they don't call the
amplitude the waveheight. I kind of think of it as a wavegap. If you
painted a big sine wave on the street and asked me how long it was,
I'd get one
of those little rolling doohickies for measuring and trace the line
through its curve. Without knowing the definition in advance, I
wouldn't think you would
be asking me the straight distance between two points of
corresponding
phase.

I ask this question because I don't understand why it's called what
it's called, not because I want to tell the experts they got it
wrong. It's bugged me for a while, so I've finally decided to take the
plunge and risk looking stupid.

Thanks in advance for any responses or links to read..."

--
Jim Carr

It is called "length" because it truly is a length.

Wavelength is usually stated as "Peak to Peak", or pp


How is it calculated?

It can be measured using an oscilloscope.


I know how to measure amplitude or time with a scope. I just can't figure
out how to measure distance.

On Wed, 16 Jan 2008 10:42:32 -0500, "Jim"
wrote:

I know how to measure amplitude or time with a scope. I just can't figure
out how to measure distance.

You don't measure distance on the scope, it measures time. Given the
speed of the wave, typically 300,000,000 meters/sec, it is easy to
calculate distance, e.g., a 1 microsecond wave equals 300 meters
wavelength.

Wayne.B wrote:
On Wed, 16 Jan 2008 10:42:32 -0500, "Jim"
wrote:

I know how to measure amplitude or time with a scope. I just can't figure
out how to measure distance.

You don't measure distance on the scope, it measures time. Given the
speed of the wave, typically 300,000,000 meters/sec, it is easy to
calculate distance, e.g., a 1 microsecond wave equals 300 meters
wavelength.

True, except when the dielectric constant (relative
permittivity) of the medium is higher than free space, then
the wavelength is reduced by 1/sqrt(Er). Common coax cable
dielectrics usually have an Er ~ 2.2 and most PC board
material is about 4.4 or so.