Making Waves

On Built on Facts, Matt Springer writes that "there's really no such thing as a purely continuous monochromatic light wave" and "any pulse of light that lasts a finite amount of time will actually contain a range of frequencies." Pass this pulse of light through a medium such as glass, which "can have a different refractive index for each frequency," and some very weird things start to happen. On Life at the SETI Institute, Dr. Lori Fenton explains her study of "aeolian geomorphology - how wind shapes a planetary surface." As it does on Earth, weather makes wave patterns in the dunes of Venus, Mars, and Saturn's moon Titan, leaving a record of the meteorological forces at play. On Uncertain Principles, Chad Orzel takes a step back from wave-particle duality. Researchers have observed wave interference in molecules that "contain up to 430 atoms, and are several nanometers across, making them by far the largest objects anybody has ever seen displaying wave behavior." This brings the "quantum-classical boundary" a little closer to the human scale. But for now, we still behave a lot like particles.

More like this

Last time we took a pulse of light and shot it through a medium with a frequency-dependent refractive index. The particular form of the refractive index was sort of interesting - for some frequencies, it was less than 1. That implied that the phase velocity of a sine wave would be faster than the…
Last time, we did some slightly boring groundwork. This time, we're going to look at something more interesting: the way a pulse of light propagates in something (like a piece of glass) with a frequency-dependent refractive index. As we discussed, the refractive index is just a way to express the…
It's been a while since I wrote up a ResearchBlogging post, but since a recent paper forced me to update my "What Every Dog Should Know About Quantum Physics" slides with new pictures, I thought I should highlight the work on the blog as well. Not that you could've missed it, if you follow physics…
I've mentioned before that I'm answering the occasional question over at the Physics Stack Exchange site, a crowd-sourced physics Q&A. When I'm particularly pleased with a question and answer, I'll be promoting them over here like, well, now. Yesterday, somebody posted this question: Consider a…

Of course Fourier theory tells us this. A pure spike contains all frequencies and an infinite wave train contains only one.
(actually the two ends of the spectrum are just the manifestation in the time and frequency domains of the same thing.