Posted for Jim Knighten:
------------------------ From: "Knighten, James L" <[email protected]> Subject: RE: Visible Light & EMC Date: Fri, 12 Mar 1999 08:45:31 -0800 To: Allen Tudor <[email protected]>, [email protected] > Allen, > > "Electromagnetic energy" in the radio spectrum doesn't travel the same way > through all solid objects. The properties of its propagation are dependent > on material properties of the solid. There are losses (conductive losses > and losses in dielectrics) and there are properties that influence > wavelength and velocity (permittivity, permeability, and even conductivity). > Some materials have different properties at different frequencies, hence > they are dispersive (some frequencies travel at higher velocities than > others). We know that some materials are good reflectors (mirrors) of radio > frequency energy (good conductors). > > So, why shouldn't the travel of light, which you assert is also > electromagnetic energy, be similarly influenced by the properties of the > solid material that it is traveling through? Some solids are good > reflectors (polished mirrored surfaces). Translucent materials are lossy > materials to visible light. Transparent materials have low loss to light. > > Radio frequency waves have longer wavelengths than visible light. One of > the consequences of this is that it is harder find solids that form infinite > planes, or are semi-infinite in a dimension. Hence, you witness more > effects caused by the edges of solids than you do with visible light. This > makes it more difficult to perform the exact "dual" experiments in both > media. > > We believe that electromagnetic energy behaves according to Maxwell's > equations. Does light? I think we do not know because we cannot perform > the same kind of experiments (make the same sorts of observations) at these > short wavelengths that we can at RF frequencies. Maxwell's equations are > macroscopic. At the microscopic level, behavior may have to be described > differently. > > Are RF and light manifestations of the same phenomenon? I think the answer > is yes. > > Regards, > > Jim > > Dr. Jim Knighten e-mail: [email protected] > <mailto:[email protected]> > Senior Consulting Engineer > NCR > 17095 Via del Campo > San Diego, CA 92127 http://www.ncr.com <http://www.ncr.com> > Tel: 619-485-2537 > Fax: 619-485-3788 > > > -----Original Message----- > From: Allen Tudor [SMTP:[email protected]] > Sent: Thursday, March 11, 1999 11:14 AM > To: [email protected] > Subject: Visible Light & EMC > > This question sounds goofy, but here goes anyway.... > > Why doesn't visible light travel through solid objects (plastic, > wood, etc)? Unless I've totally missed the boat, visible light is > electromagnetic energy beginning at about 100,000GHz. So why doesn't it > behave like electromagnetic energy in the radio spectrum? My guess is that > it has something to do with the wavelength vs. the thickness of the object. > > > > Allen Tudor, Compliance Engineer > PairGain Technologies tel: (919)875-3382 > 2431-153 Spring Forest Rd. fax: (919)876-1817 > Raleigh, NC 27615 email: > [email protected] > > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > > ---------------End of Original Message----------------- -------------------------- Ed Price [email protected] Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 List-Post: [email protected] Date: 03/12/1999 Time: 11:50:54 -------------------------- --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
