One of the interesting things about a video camera is the effect its sequential shutter has on moving objects. A video (or a movie) is a collection of still frames played back rapidly enough that your visual system doesn’t detect the gaps between the images. Each image is a slice of time, but when those slices don’t match the movement of an object you get some interesting effects. (Ever watch a video of a moving car where the wheels look like they’re turning backwards? That’s a good example of the phenomenon.
One experimenter took it a step further. He attached a hose to a speaker, which when fed with a continuous tone caused the end of the tube to vibrate. When water flowed through the tube, it was moved back and forth at the same rate as the tube. By varying the frequency (pitch) of the tone being sent through the speakers, he could vary the rate at which the stream of water was deflected.
Here’s the cool part: if he matched the frequency (in hertz) to the frame rate of a video camera, he could make the water look like it was hanging in mid-air! Even better, by varying the frequency of the tone even by a single hertz, he could get the water to appear to flow backwards.
Watch and be fascinated.
-=[ Grant ]=-