April 13, 2014

Wow your friends with this great demo!  It looks like this string is dancing in slow motion and you can control the speed of its dance moves.  It’s not just cool, it’s science:)

 Episode 8: Dancing String

(Standing Waves part 1)

Isn’t that Great?!!!

Like I said in the video, it’s really just an illusion.  That string is moving back and forth really fast and the strobe light just makes it seem like it’s moving slowly–or like it’s dancing.  A strobe light is a light that flashes on and off really fast.  In the dark room the video camera only “sees” the string when the light flashes on.  I can adjust how quickly it flashes.  So I can adjust it so that the light blinks on exactly when the string is back in the same spot it was at the last flash (even though it moved down and then back up).  That makes it look like the string hasn’t moved.  I can also make it flash a little slower so that on the next flash it looks like the string is just below where it started (the string moved down  and then up and then down just a little more).  That makes it seem like the string is slowly moving down.  Or I can make it flash so that the string looks like it’s barely moving upwards.  It’s the same sort of effect as when it looks like the wheels of a car on TV are spinning backwards.  The first part of this video shows that illusion (you can watch the whole explanation if you want, but it does get a little math-y).

Even though the dancing part is an illusion the fact that the string doesn’t move back and forth in the middle is not–that is just cool physics…but more on that next time.

This is the first video of a series of three about standing waves.  Look for the next video soon explaining the science behind them.  The third video will be how to make a standing wave jiggler to impress your friends. 

Get Stoked About Science!