Double slit experiment (one slit closed)

[Born2bwire]

The images I posted are the maximum value of the electric field the x-z plane along changing x (now that I think about it, I really should have taken the maximum of the absolute value but since I have a single sinusoidal source this shouldn't matter). It was done emulating the same tests that buffordboy did. Two slits, 100 wavelengths apart. The only difference is that I needed to try and be in the far-field since he was using a Fraunhoffer (stupid optics people) approximation while my code is a full wave solver. So my plots are taken something like 133 wavelengths away from the slits. Not ideal but each time step only advances the wave by about 0.354 cells. So for a 1480 cell long problem space, it takes 8372 time steps for the wave to fully traverse the length and back again. So time is a bit of a problem, it took around 10-20 minutes to run 8000 time steps for a 1200x1480 problem space. I might be able to improve on this, I use field-splitting for the perfectly matched layer at the boundary but technically I only need to split the field in the PML layer, which is only 25 cells deep. So I could save a lot of memory and a one or two memory access and writes for each cell per iteration by fixing this. The only other difference is that his plots are respect to the angle where mine would be the equivalent of projecting his plots onto a flat plane.

The details of the movies are given in the description of the videos but, they are a 500x500 cell problem space with plane wave sources. Each cell is 0.25 wavelengths (125x125 wavelengths). The slits are separated by 200 cells (5 wavelengths) and are 1 cell (1/25 wavelength) and 75 cells (3 wavelengths) wide respectively. I wanted to show you how different a sub-wavelength and sup-wavelength slits are. These are also in the near-field but you can see how quickly the interference pattern sets up. You could print these out, draw and measure the angles and get a favorable comparison with what you would expect from theory.

I think though, that the primary reason for asymmetry is the fact that a larger slit will have a much larger amplitude sourcing from it. The first two videos I posted are on the same scale, so you can see how much more area the resulting waves from the larger slits clip the scale. If the field values are greater than the limits of the scale, then the field is just shown as red/blue.

 

[Volcano]

Born2bwire, thank you again. Actually, your last three graphs are fit to my previous expectation. I want to be sure. But I want to learn the amount of diffraction effects to results from large slits. I don't know the math you used to come this result(graphs). Can you try the same calculations with smaller slit widths? For example, left slit 0.05 wavelength and right one 0.1wavelength widths. Of course, a 0.1-0.1 wavelength couple slit widths graph would be better to compare. And every time slit spacing 100 wavelength. I select these because they are enough values to avoid diffractions. Again; I don't want simulations because these are very small values to draw easily. I will be contented with picture of graphs.

And finally, if possible I would like to learn the equation(s) especially which contains slit widths. I suppose you didn't use the same equations which buffordboy used(showed). Otherwise the graphs would be identical.