### Strobe Fountain

```http://www.youtube.com/watch?v=bpb
t-ICK58g
 http://videosift.com/video/TimeFountain-Water-Optical-Illusion


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.

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.

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.

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.

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.

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

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

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.





http://exs.exploratorium.edu/exhibits/strobe
-fountain/
boscopic-effect.html
http://www.exploratorium.edu/xref/exhibits
/strobe_fountain.html
http://www.cre.ations.net/creation/thetime-fountain
```