|
Activity
13. Photographing splashes
Equipment needed:
Vivitar 283 flash unit
4 AA batteries or SB-4 AC adapter
Cord to connect flash unit to delay circuit
Flash clamp
Interrupter-style photogate (Schmitt-triggered type) and cord
to delay circuit
Electronic delay circuit with 0.5-µf capacitor
Support stands for interrupter
Milk, dropper, ball, bucket of water or aquarium tank
The interrupter-style Schmitt-triggered photogate described in
the Tools
section works best for this activity. Set up the interrupter
about a foot above the table top. Connect the output of the
photogate to the input of the delay circuit, and connect output 2 of
the delay circuit to a flash unit. Adjust the photogate for maximum
sensitivity. Release a milk drop just above the gate. Adjust the
delay so that you can capture the drop as it strikes the table. The
0.5-uf capacitor will provide delays up to about a half second.
If you're taking photos, you may find that the splash of the milk
drop is so small that you can't get a large enough image on film. In
order to produce a bigger splash, drop a ball into a bucket of
water. By adjusting the delay, you should be able to see the
circular wall of water that forms as the ball is breaking the
surface. At slightly later times, you may be able to capture the jet
of water that rises vertically as the water rushes inward to close
the cavity formed by the ball. If you drop the ball into an aquarium
of water and aim the flash unit through the side, you can adjust the
delay to see the path of the ball in the water.
|
