Don Kerr wrote:
>
> Sooooooooo, what's yer point ?
>
> Mike Frerichs wrote:
> >
> > Sorry to have to point this out also, but you're confusing audio waves with
> > electromagnetic waves. They have nothing at all to do with each other.
>Audio
> > waves are just waves of compressed air (or water, or any other physical
> > substance), which for humans, are in the general range that you mentioned
>(20 -
> > 20KHz). Electromagnetic waves, on the other hand, are what is generally
> > referred to as radiation. The other items you mentioned (Radio, Micro,
>Infrared
> > (heat), Visible Light, Ultraviolet, X, Gamma, Cosmic) are all
>electromagnetic
> > radiation.
> >
> > Mike Frerichs
> >
> > "Lin, Gary" wrote:
> >
> > > The electromagnetic wave spectrum starts at Audio (0 Hz, though you
> > > generally don't hear <20, to 20 KHz) then goes through Radio (20 KHz
> > > -300,000 MHz), Micro, Infrared (heat), Visible Light, Ultraviolet, X,
>Gamma,
> > > Cosmic. Wavelength starts at infinity and shortens as frequency
>increases.
Unintentionally, I suppose, Gary is partly correct. While not audio,
electromagnetic waves in extremely low frequencies are now commonplace,
being used in frequency ranges from 8-80 Hz, by the US, Great Britain,
France and the former Soviet Union for communications with submarines
when those ships are too deep for satellite signals. As well, ELF is
generated naturally in the ionosphere, at frequencies reportedly as low
as 300 Hz.
Now, as for the business of highly chromed surfaces attaining higher
temperatures than white surfaces when exposed to the sun -- this is
largely due to the relative reflectivity of the material. Some small
percentage of the sunlight is not reflected, and this portion is
converted to heat, as with other absorbers. Unlike other absorbers, the
high reflectivity creates a sort of greenhouse effect under the
reflective layer, because it is reflective on both inner and outer
surfaces. Heat is reflected back into the base material, so its
temperature rises with continued exposure to sunlight. Moreover,
chromium is not a good radiator of heat.
Motorcycle riders will attest to the value of chrome exhaust pipes--one
can get quite close to the pipes without being burned, because the heat
radiated from the surface is quite low. Touch the pipes, however, and
expect to be seared....
Cheers.
|