Deejay Cork

Our Physics seminar today was funny.
We were talking about waves. Ms Kolzrtova got a feeling I was dreaming (I actually was), so I had to extract the formula for composing two waves :-)
What we're doing next was even better. It was an experiment to show the sound waves. We filled a long tube with cork powder. Then we were emitting sound with a nearby sound reproducer. Ms Kolzrtova was changing the sound frequencies and when she reached the right one, cork in the tube began vibrating. It was an amazing performance!
But that's not all. We called her Deejay Cork, cause when she was tuning the frequencies, it actually sounded much like music (if you consider techno a kind of music :-)