Interesting things happen when you combine makering with photography. Take this project by science channel brusspup for example. He has a neat way of making water flow in some weird ways, with the topping on the icecream being making them flow backwards.
So, how does it work?
The first part is tone generator. Brusspup is using a homemade device for that, but you can use an online tone generator. Tones are generated at 24Hz (that is 24 peaks a second). Those tones are fed to a hose via a speaker. Now the hose is generating a waveform, but we can’t see it because it is constantly changing.
The second part is the camera, which runs at 24 frames per second. You can think of a 24 FPS camera as a stroboscopic device that takes 24 images a second and freezes them.
When you combine the two you, the camera freezes the waveform like a strobe. Here is the cool part. Running the water with a 25Hz frequency will make them seem like they are flowing forward. Using a 23Hz frequency will make the water seem as they are flowing backward. (and you get 5 karma points if you can explain why).
P.S. – we took the liberty to prepare some wave files for you: