I heard a public talk about doppler weather radar today, and have some
questions. A fair amount of time was devoted to radar signals bypassing
targets or reflecting off them. It was pretty clever. The dependency was
generally the relationship of the object's size and the length of a wave.
Polarization had some effect.

Can someone give me an idea, a simple reason or example why, for example, if
the wavelength is much shorter than the target's size, the wave will bounce
off it, and scatter from a larger object? Apparently, polarization occurs
when the wave length is much larger than the object. How does polarization
help detect certain types of objects?

Is there a fairly introductory book to these subjects or a website? The
presenter made himself very clear about how this works without much use of
math. One equation.
--
W. eWatson

(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Web Page: www.speckledwithstars.net/

One site to try

http://www.radartutorial.eu/01.basics/rb04.en.html


Since electromagnetic (EM) radiation is both a wave and a particle the
wave nature
mandates that an object be at least a 1/2 wavelength in size to react
with an EM wave.

On Feb 14, 9:13*pm, "W. eWatson" wrote:
I heard a public talk about doppler weather radar today, and have some
questions. A fair amount of time was devoted to radar signals bypassing
targets or reflecting off them. It was pretty clever. The dependency was
generally the relationship of the object's size and the length of a wave.
Polarization had some effect.

Can someone give me an idea, a simple reason or example why, for example, if
the wavelength is much shorter than the target's size, the wave will bounce
off it, and scatter from a larger object? Apparently, polarization occurs
when the wave length is much larger than the object. How does polarization
help detect certain types of objects?

Is there a fairly introductory book to these subjects or a website? The
presenter made himself very clear about how this works without much use of
math. One equation.
--
* * * * * * * * * * * * * * * * W. eWatson

* * * * * * * (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
* * * * * * * *Obz Site: *39° 15' 7" N, 121° 2' 32" W, 2700 feet

* * * * * * * * * * *Web Page: www.speckledwithstars.net/

wrote:
One site to try

http://www.radartutorial.eu/01.basics/rb04.en.html


Since electromagnetic (EM) radiation is both a wave and a particle the
wave nature
mandates that an object be at least a 1/2 wavelength in size to react
with an EM wave.

On Feb 14, 9:13 pm, "W. eWatson" wrote:
I heard a public talk about doppler weather radar today, and have some
questions. A fair amount of time was devoted to radar signals bypassing
targets or reflecting off them. It was pretty clever. The dependency was
generally the relationship of the object's size and the length of a wave.
Polarization had some effect.

Can someone give me an idea, a simple reason or example why, for example, if
the wavelength is much shorter than the target's size, the wave will bounce
off it, and scatter from a larger object? Apparently, polarization occurs
when the wave length is much larger than the object. How does polarization
help detect certain types of objects?

Is there a fairly introductory book to these subjects or a website? The
presenter made himself very clear about how this works without much use of
math. One equation.
--
Thanks. That's quite a good site. It has one drawback, moving forward
easily. Each page is so big, I have to scroll down to find the "next". I
have acrobat, so I think I can convert this to a pdf. That would help.

Ah, duality. Yes. I have several popular physics books and they mention the
concept of wave length and object size, but never mention waves can be
described as particles. For one example, Thinking Physics. I just loaned it
to a neighbor, so can't give the specifics.
--
W. eWatson

(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Web Page: www.speckledwithstars.net/

On Feb 15, 12:51*pm, "W. eWatson" wrote:
Apparently, polarization occurs
when the wave length is much larger than the object. How does polarization
help detect certain types of objects?

On to polarization: If an objects dimension is larger in one direction
than another (perpendicular to the radar)
then backscatter polarization increases. A squashed raindrop tends to
return a higher polarization than a spherical one.
Likewise a bird or insect with its wings extended.

wrote:
On Feb 15, 12:51 pm, "W. eWatson" wrote:
Apparently, polarization occurs
when the wave length is much larger than the object. How does polarization
help detect certain types of objects?

On to polarization: If an objects dimension is larger in one direction
than another (perpendicular to the radar)
then backscatter polarization increases. A squashed raindrop tends to
return a higher polarization than a spherical one.
Likewise a bird or insect with its wings extended.

What reflections cause circular polarization?

I did a little searching on the web regarding wavelength and object size.
This came up http://www.physicsforums.com/archive/index.php/t-177295.html.
I re-borrowed my Thinking Physics and found where the author deals with a
similar question. He asks which is smaller, an atom or light wave. He
proceeds to answer it by discussing light reflecting off a polished mirror,
but goes no further.

--
W. eWatson

(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Web Page: www.speckledwithstars.net/

On Feb 17, 12:56*am, "W. eWatson" wrote:

What reflections cause circular polarization?

If I recall correctly "circular polarization" means no polarization.

I forgot to mention that ice-crystals that align in wind can also
polarize radar returns.

He asks which is smaller, an atom or light wave. He
proceeds to answer it by discussing light reflecting off a polished mirror,
but goes no further.

When you consider also that a particle (atom) also has a wave function
I start to get a headache thinking about these things....

Trying to visualize things is higher than 4 dimensions is not my
specialty...

wrote:
On Feb 17, 12:56 am, "W. eWatson" wrote:

What reflections cause circular polarization?

If I recall correctly "circular polarization" means no polarization.

I forgot to mention that ice-crystals that align in wind can also
polarize radar returns.

He asks which is smaller, an atom or light wave. He
proceeds to answer it by discussing light reflecting off a polished mirror,
but goes no further.

When you consider also that a particle (atom) also has a wave function
I start to get a headache thinking about these things....

Trying to visualize things is higher than 4 dimensions is not my
specialty...
I know what you mean about four dimensions. Here's something startling about
extra dimensions. Circumscribe a circle inside a square, then a sphere
inside a cube, then a 4-d hypersphere inside a 4-d hyper cube, ..., then a
10-d hypersphere inside a 10-d hypercube. In the last case, it can be shown
that the sphere protrudes outside the cube. It's pretty straightforward
mathematics using simple geometric concepts, sums of squares, etc.

Epstein's question has a simple answer that's attractive, "...atom must be
smaller than light waves by reflection. If atoms were not smaller, it would
be impossible to make a surface smooth enough to give a good reflection. If
a reflection...". He then spends a few sentences on radio telescope's
roughness, and the size of wavelengths. Not entirely satisfying but not bad.

The physics forum link shows an almost a frequency band by band or particle
size by size description.

--
W. eWatson

(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Web Page: www.speckledwithstars.net/