I saw this video on “Videos I found on reddit” where this guy had salt or something on a table, and he had this thing he rubbed on the table that made a sound and moved the salt into a star like shape, then he used a different object that made a deeper tone that moved the salt back, can anyone explain this? If needed i can provide a link and timestamp
In: Physics
There are 3 concepts here.
One, “tone” of a sound is its frequency, which is how many times per second the soundwave vibrates. A sound wave goes through its whole amplitude within a fraction of a second. Accordingly, there is also a wavelength, which is the distance the sound travels in that same fraction of a second.
Two, soundwaves bounce within objects. A table has a certain length which is a multiple of some wavelengths. Those wavelengths can bounce back and forth within the table and the overall wave will be “locked” in place. Depending on wavelength, size and shape of the table, they will create patterns: in some parts the wave is strong, in others there is none.
Three, small grains of salt vibrate where the wave is strong. This gives them energy to randomly move. The random move has a chance to move them into a part of the table where the wave is very weak, where they no longer have the energy to move farther so they just stay there. (It is the same as debris on the road accumulating next to the curbs – if it’s in the middle of the road it gets hit by passing cars and moves to another random place, but once it’s on the side there are no cars there to hit it back into the middle)
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