Recent content by Andy Resnick

This is a sample of an ultramafic rock: I think this is either a phlogopite-hornblende-olivine peridotite or a pyroxene peridotite- I had (and still have) trouble distinguishing between pyroxene and amphibole in this sample. Major minerals: serpentinized olivine phenocrysts, horneblende or...

Asking on behalf of a colleague who is studying rainwater transport/drainage in the context of plants (trees, mostly): There's a lot of published work analyzing the flow of fluid within a tube, or along an interior corner. I can't seem to find much of anything about the flow of water along the...

Now I understand why you keep insisting on gaussian beams. I'm sorry, but this does not demonstrate to me that you can evaluate basic integrals.

I'm concerned we are not making progress here. To proceed, I need to know that you can evaluate the Fourier integral F(k)=∫f(x)eikxdx when f(x) is a plane wave with wave-vector k'. I also need you to provide evidence (for example, a calculation) that verifies your claim "If you place a...

Be careful- the FT does not just happen, it is a consequence of Fraunhofer's approximation to the Rayleigh-Sommerfeld diffraction formula. You had me, then you lost me. The function δ(k-k') does not mean that if k ≠ k', there are equal numbers of positive and negative points. It does mean...

I don't know what you mean by "real understanding". A lens doesn't always perform a Fourier transform. What a lens *can* do is bring the far-field a lot closer. How about this- evaluate the Fourier integral F(k)=∫f(x)eikxdx when f(x) is a plane wave with wave-vector k'. What is the result...

I think this is making the situation too complex: light reflecting off a mirror is an example of an elastic collision, for example.

Unfortunately, the comet is too close to the horizon line (here).

Maybe it would help to think of "the far field" as Fourier transform space (equivalent to 'k-space' in scattering) of the object plane; a single plane wave is of infinite extent and has a single wavevector and thus transforms to a single point. If that plane wave is instead truncated by an...

I had a chance to take a few careful images of arfvedsonite crystals today, I think I found an arrangement with both 'head cut' and longitudinally oriented crystals in the field of view. Here's a photo with just the (EW) analyzer present: On the right side, the crystal is in the 'head-cut'...

Last night I realized I need to be more careful in my polarizer description/analysis. The polarizer may indeed be oriented NS, but then the analyzer is EW, so for PP imaging I may need to be more specific about which polarizing element is in the path... stay tuned!

Don't mix up energy and momentum- momentum is a vector, for example. In an elastic collision, changing the direction of propagation requires a change in momentum but no change in energy.

Now I'm motivated to try putting my M2 extension tube on the 800mm lens and turn it into a bizarro macro lens... :)

Interesting... do you know the image circle size of your scope? Does it support a 35mm full frame format image?

I was wondering if that's the case. Is it an alteration product? My understanding is that these rocks are all very silica-undersaturated.