Magnetically Controlled Reflection of a Ferrofluid Cell



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Figure 13 – Notice that the pattern seen in the ferrofluid continues across bubble.
Changing gears to Figure #13, there are two things to notice. First notice that the hysteresis shaped pattern(s) continue even thought that the there is a bubble of air inside the ferrofluid cell. Clearly the image is truncated at the ferrofluid/air interface with little edge distortion yet the image reappears on the other side of bubble. Notice at this camera angle, the mirror does not show an reflection.
Another observation is that there’s a flaw on the glass surface around 1’oclock that is casting a shadow seen at the top right center of the cell. There is no sign of light from other parts of the cell bleeding into the shadow area. I claim that the border of the shadow is well defined, and this argues against Diffraction being the primary cause of the hysteresis shape.



Figure 14 – Showing magnetically controlled absorption of blue light.
Note that the lack of scatter signal from a shaded area of the cell does prove a lack of resonance at that location, because without incoming photons how can you have scatter?
Figure #14 is just the blue channel of the RGB photograph of Figure #13. Cameras detect photons on three different color channels and we can turn off the red and green and just look at the blue. Clearly we can see that where the red lines show up in Figure #13 that a ‘lack’ of lines show up in Figure #14.
If you compare the red channel and the blue channel, you would find that they are inverted images of each other in regards to the hysteresis shaped patterns. We can say this is blue light extinction or absorption or non-reflection but clearly the photograph is missing some blue photons. Note the white dust on the ferrofluid cell in the black areas of Figure #14, this shows that the camera is working correctly, and that the blue light levels of hysteresis shaped patterns are below the baseline blue light levels!
I was able to get my Ocean Optics PC1000 spectrometer working and was able to get some readings. My incandescent light source is a 1000 watt bulb salvaged from surplus equipment. I also used a green laser pointer to verify my calibration.

Figure 15 - Spectrum readings from a Ocean Optics PC1000 spectrometer.


The black line of the Figure #15, is the spectrum of the incandescent lamp and the green line is the spectrum of a green laser pointer. These are scaled to fit onto the graph.
The teal line are the readings with the lamp turned on and the probe resting on top of the cell which is 6mm over the ferrofluid layer. Surprisingly the ferrofluid layer is always scattering light around the 700nm range. Not surprising is that much more red light is being scattered than blue light. Comparing light in to light out; there are very few blue photons being scattered to the camera and/or the spectrograph probe.
When we apply a magnetic field and align the red lines that show up in the images under the spectrograph probe, the result is the red line of Figure #13. Notice around 550nm the red line dips below the teal line. This is consistent with Figure #14 and the depletion of the blue photons.
The red line and teal lines have the same scales. If we look at 600nm, we can see there is a lot of red photons coming from the source that are not getting scattered to the camera but at 800nm which has lower intensity levels from the source, the ferrofluid cell scatters many more of the supplied infrared photons.
Just going by the graph, I can tell that the ferrofluid cells are more efficient at scattering near-optical infrared frequencies than they are at optical frequencies. It's like looking at an iceberg and realizing that the iceberg is larger below the water line. In other words, after seven years am just starting to realize what a ferrofluid cell can do.

Figure 16 - Baseline NIR reading at 45 degrees incidence divided by source spectrum.




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