Recent content by Gobil

hmm, after much fiddling around I´m pretty sure I´m putting in the right values, but for the diffraction pattern of a square aperture is the image you see below, which seems like one quarter of the real image or something like that. any ideas?

ok, thanks jtbell, the applet is useful, as you can see from my image, it looks like I´m just getting one corner of the actual diffraction pattern, which I don´t understand very well. I did read somewhere when doing Fourier transforms you get a one sided spectrum and have to reflect it, but I´m...

hi All, I recently got interested in a general solution to diffraction from an object at verious distance and wavelengths. I came across the Fresnel Kirchoff formula (attached formula from Schnars, digital holography). My problem is I cannot seem to replicate a diffraction that makes...

I guess so. The scenario is as follows, you have an opaque slit normally like metal, for example, to use in a spectrometer. then you just replace this slit with glass, which is transparent to the light in question. what happens at the edges? I´m not so concerned obout what kind of pattern you...

hi All, I got to thinking recently about diffraction; through an opaque slit for example, causes a normal diffraction pattern which is well described in texts. However, what happens when you have slit transparent to the light which is going through it. Obviously, the light passes through the...

I see, it´s not that I have a problem with the wave treatment, it´s just I have an image of the the transverse electric field and how it´s affected by the gradient. i.e. slowed down in one of the transverse directions and bent in that direction. but I´m not sure if this is right.

hmm, Fermat´s principle is simply a rule to follow. The question can be re-phrased: what is the microscopic reason for Fermat´s principle?

Good post thanks! something is still missing for me though, why, microscopically, does it go towards the slower regions? does the phase velocity suffer a drag there and hence tends towards that region?

I think this is incorrect, and it´s just the way the graphic looks. for example see the attached image, from: http://www.grintech.de/gradient-index-optics.html it shows all the perpendicular rays being bent, which is the principal of these optics

From what I've read this is not true: wiki GRIN lenses. They focus light by having a refractive index gradient inside the material. The actual optic is cOmpletely flat, and the light enters perpendicular to the gradient. I just can't find an equation to describe this. Or a picture of what's...

thanks for the responses guys. so, ignoring density for a while, and just thinking about the refractive index gradient, let's assume it´s a linear change in space perpendicular to the beam propagation direction. The light bends towards the slower part, i.e. it will tens to bend to the places...

Hi Folks, After a general search online, I have not yet found a simple description of refraction in a medium with an inhomogeneous refractive index. For example: if we have a block of glass with a beam of light shining through it, and the block has a gradient in the real part of the...

hi again, Looking at PRB, 40, 6, I see a treatment of the Lindhard function. Here they describe the response function of the free electrons (equation 1). But I am still confused about the symbols and what to put in. They have the FD functions in terms of k and k + q. k is the electron...

I´m sorry, physically I just don't get it. In an infinite isotropic, homogeneous medium, why does the light see a different refractive index depending on what direction it is propagating??

but in an isotropic material with mu = 1 do we also need this description? also, is this only valid for waves incident on a surface? i.e. we are going from vacuum to some material, otherwise, if we are in a infinite isotropic homogeneous medium, the direction of the k vector does not matter...