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Zone plates, moiré patterns, and more!
This is an app created to physically manipulate molecules using so-called "optical tweezers," said tweezers having been invented by the current US Secretary of Energy, Steven Chu, garnering him the Nobel Prize in Physics.
You won`t be tweezing any molecules with this app, since you`re likely lacking the few hundred thousand dollars worth of "peripherals" needed, but you can explore a bit about zone plates, moire patterns, and holography.
The round balls on the screen are what you use to manipulate the colored pattern on the screen. You banish a ball by double-tapping it. You make a new ball appear by double-tapping the screen background.
Start out by banishing two balls. Now manipulate the ball that`s left. Move it off-center, so it is in the right quadrant (left quadrant if you`re a lefty). You`ll see a bunch of straight bands or stripes. Now, start growing the ball by putting two fingers in it and pulling them apart. You`ll see that the colored bands bend and eventually become concentric circles around a large open center. Note that the bands get closer and closer together as the rings go outward. This object is called a "zone plate," and it is a naturally-occuring, fundamental wave-form. Drop a stone in a still pond and you`ll see this exact same shape, with the waves getting closer and closer together. Drop a boat in a still lake and you`ll see the same thing. Start moving the boat, and you`ll get a series of concentric rings. Move the boat fast enough, and the boat will outrun its own rings. In that case, the rings build up in front of it, pushed by the boat, and then trail off to the sides, what we call a wake. Some thing with aircraft, but, in their case, the rings are sound waves. Outrun sound and you`ll get a wake just like the one from the boat. People on the ground experience the wake as it passes over them as a single loud boom, a sonic boom. Tsunamis (tidal waves) are also zone plates, their energy racing outward in ever more compressed rings.
Holograms consist of millions of zone plates, each eminating from a single point of light. Look at a photographic hologram and you`ll see many large zone plates. Those are coming from dust particles very close to the film. The objects further away have their lines so close together you can`t perceive them with the naked eye. This app was designed to generate holograms that are used to aim lasers at nano-sized objects to manipulate them, hence optical tweezers.
Now, stretch the ball out much farther, until it is taking up much of the screen. Notice how some "phantom" zone plates appear toward the top and bottom of the screen. The bands are "interfering" with the pixels making up the screen. Television suffers from this. Personalities are warned not to wear certain kinds of stripes and checks or they can interfere with the pixels in the camera, causing what`s called "strobing." These patterns are called moiré patterns. You see them in certain materials, like silk or rayon, when multiple layers overlap.
Stretch the control ball further, until it is larger than the screen. More and more zone plates will appear. Note the spaces between the zone plates. Now, there are many "phantom" zone plates, representing places where the bands of two plates are either both present or both absent. If this were water, the spots where both are present would have uncharacteristically high waves and where both absent would have uncharacteristically deep troughs. "Rogue waves," those up to 200 foot high collosal waves capable of sinking a large modern cruise ship, arise from just this sort of interference.
Keep going, and the screen will be completely filled with little balls. Expand it further and, every so often, a new large pattern will appear. When two layers of material have the same pattern and you rotate them against each other, you get a magnification of the underlying pattern. Try this with semi-transparent fabrics or window screening material.
Now, get rid of that control ball by double-pressing it. The screen goes black. No, it hasn`t crashed. Double-press again and you`ll get a new ball. Now, slightly enlarge it and start twisting it. You`ll see the color pattern begin to twist as well. Keep most of the control ball off the screen (so it doesn`t cover up and mute the pretty pattern again) and keep twisting. Then, make the colored spiral spin by pinching and stretching the control ball. Now, you`re on your own...
Fun, easy to figure out, and it`s ingenious.
You can make really cool looking designs easily you don`t learn about holograms and the twisting control on the dots is a bit annoying because the dots are almost impossible to make them fracture the light but I think it`s still cool
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