inspired by a chladni plate experiment

[asakiyume]

In this video, a guy pours couscous over a plate and plays the edge of the plate with a bow to make musical vibrations, which then causes the couscous to move into beautiful patterns.

Watch on YouTube

This inspired me to try similar, except I don't have a thin metal plate or a bow--or, right at the moment, couscous. What I do have is a cookie sheet, rice, and a saw. So!

Here's the rice on the cookie sheet:



Here it is after I shook the tray back and forth. The way I was shaking it, the rice all clustered together like a murmuration of starlings:



Here's a roll of duct tape on the floor. I'm going to set the tray on it and then bang the saw over the top of the tray:



Here's the tray in place ...



And here's how I'm going to bang the saw:



And here are the first results!



Not exactly symmetrical, but still very interesting! The rice collects where the sheet is *not* vibrating.


before


after


before


after


I am so science!!

Comments

[sovay]

Not exactly symmetrical, but still very interesting! The rice collects where the sheet is *not* vibrating.

Science!

That is neat. I have seen similar demonstrations done, but not with couscous. Or rice.

[asakiyume]

There's a funny moment in the video where the guy hastens to add that it should be *uncooked* couscous. Similarly with rice.

[duccio]

Why don't you try using an electric razor (or a vibrator, should you happen to have one). It looks like he touched the edge of the plate here and there to get different patterns. Those are probably the nodal points to activate the harmonics of the plate - like harmonics on a guitar string, or a wind instrument's harmonic series, like for instance, on a trumpet.

I'm so science, too.

[asakiyume]

I like that idea--I'll do it, and then I'll post the results.

[a_muse_d]

:D

[asakiyume]

^_^

[cmcmck]

Amazing stuff couscous but who knew just how amazing? :o)

[asakiyume]

LOL, well, I think sand, sugar, bulgar wheat, millet, pearl barley etc. might work equally well but yes! Apart from responding to vibrations in lovely ways, couscous is definitely amazing!

[pameladean]

You are totally science! I do wonder how people think of these things to start with.

I also wonder, after the comment immediately preceding this, what a mixture of different dry grains and sugar or whatever would do. Or maybe salt; then you could still cook them afterwards.

P.

[asakiyume]

I tried it first with semolina flour, which was too fine; it clumped up--but I did then cook the flour, as it happens! It would definitely be interesting to see how grains of different sizes and shapes acted, maybe first on their own and then mixed together. I wonder if they'd arrange themselves in layers or whether they'd all be mixed in. I GUESS I HAVE A WAY TO FIND OUT.

[gaudior]

That's so cool!

[asakiyume]

"And that's why I could never work from home," concluded one of the women in my book group when I told them about doing this.

"Haha, yeaaahhhh..." I said. But it was a worthwhile distraction, I think.

[cgbookcat1]

When I teach the unit on waves to my college students, I always do this demonstration (with a fine sand). However, we have a tunable oscillation generator so that the entire thing bounces a bit, and no bow is necessary. At resonances the system gets very loud! It's a lot of fun to slowly turn up the frequency and watch patterns form, disappear, and be replaced by new ones. There are pattern differences between plate shapes, too -- we have a square and a circle.

[asakiyume]

How cool! I may have to find a way to get a bow, and also a thinner, less warped metal surface, because I really want to see something a little closer to the chladni resuluts.

I tried using an electric razor to make the vibrations, as duccio suggested, but it just caused the rice to congregate on the side of the tray under which I was holding the razor :-\ It could be that the rice grains are too big, too--I could get some actual couscous, which is much finer grained.