Strobe Fountain

1. Strobe Fountain Done By: Chan Medric (3a305)

2. Video • http://www.youtube.com/watch?v=bpbt-ICK58g • http://videosift.com/video/Time-Fountain-Water-Optical-Illusion

3. Description • The Strobe Fountain exhibit is based on the stroboscopic effect. • Under normal light, a falling droplet is visible all along its path, and we perceive it as a falling droplet. • Under a stroboscopic light – which is darkness most of the time with brief flashes of light at regular intervals – the droplet is falling in darkness and illuminated every few milliseconds.

4. Description • Droplets collapse into spherical shapes after the nozzle because of surface tension. • Interval is constant • Flashing the strobe light at the same water falling rate makes it appear to be in mid air. • Increasing or decreasing the strobe frequency affects how the droplets move.

5. Stroboscopic Effect • It is a visual phenomenon that occurs when continuous motion is represented by a series of short or instantaneous samples. • Suppose an object is rotating at 60 revolutions per second • If it is viewed with a series of short flashes at 60 times per second, each flash illuminates the object at the same position in its rotational cycle, so it appears that the object is stationary.

6. Stroboscopic effect • If the same rotating object is viewed at 61 flashes per second, each flash will illuminate it at a slightly earlier part of its rotational cycle. • Sixty-one flashes will occur before the object is seen in the same position again, and the series of images will be perceived as if it is rotating backwards once per second. • The same effect occurs if the object is viewed at 59 flashes per second, except that each flash illuminates it a little later in its rotational cycle and so, the object will seem to be slowly rotating forwards.

7. Stroboscopic Effect • At this exhibit, a small spray of water can be observed beneath a flashing strobe light which allows visitors to see a “frozen” S-shaped pattern. In normal light only a blur of water droplets is visible, but when the strobe is flashing, the visitor can see interesting stroboscopic effects.

8. Stroboscopic Effect • If the time interval between flashes changes, we can make those apparently suspended droplets move slowly up or down. • If the interval is shortened, the droplets don't quite reach the positions of their predecessors by the time the next flash occurs, so we see the positions of the suspended droplets slowly moving upwards. • If the interval is lengthened, the droplets appear to move downwards instead

9. Wagon-wheel effect • It is an optical illusion in which a spoked wheel appears to rotate differently from its true rotation. • The wheel can appear to rotate more slowly than the true rotation, it can appear stationary, or it can appear to rotate in the opposite direction from the true rotation. • Often seen in movies in motion of fan blades and car wheels

10. Glossary • Strobe Light – A device use to produce regular flashes of light • Frequency - Frequency is the number of occurrences of a repeating event per unit time.

11. References • http://exs.exploratorium.edu/exhibits/strobe-fountain/ • http://www.ehow.com/about_5108375_stroboscopic-effect.html • http://www.exploratorium.edu/xref/exhibits/strobe_fountain.html • http://www.badscience.net/2006/09/time-distortion-strobe-fountain-thing/ • http://www.cre.ations.net/creation/the-time-fountain

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