1. Member
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Feb 2004
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50

## Diving hell-p

Hey, my husband and I are in a discussion about "sound travelling faster underwater". It says this in his scuba diving manual. As a physics-sudent/nerd, I do not understand why this is, as light/ waves slow down in a medium with a higher refractive index. n=c/v
In my optics class we applied this formula to light waves/sound waves/ seismic waves. Am I wrong? Because according to this, it travels slower. hmmmmm and what assumption did I do wrong?

2. Order of Kilopi
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Nov 2002
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## Re: Diving hell-p

Originally Posted by kelly
Hey, my husband and I are in a discussion about "sound travelling faster underwater". It says this in his scuba diving manual. As a physics-sudent/nerd, I do not understand why this is, as light/ waves slow down in a medium with a higher refractive index. n=c/v
In my optics class we applied this formula to light waves/sound waves/ seismic waves. Am I wrong? Because according to this, it travels slower. hmmmmm and what assumption did I do wrong?
Simple answer. Different kinds of waves. Light waves are electromagnetic in nature and require no medium to propagate and move at c in a vacumn. When they encounter a medium with a higher refractive index than a vacumn, they interact with the medium and there is a delay caused by the interaction, thus slowing the speed below c in a vacumn. Sound/sesmic/etc are mechanical waves and requrie a medium to travel. Mechanical waves generally move faster in a denser medium.

3. The speed of sound varies in different media, about 300 m/s in air, 1500 m/s in water, and 5000 m/s in iron. I'm still trying to work out the refractive index of iron.

4. Established Member
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Jun 2002
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Scubastronomy?

5. Originally Posted by A Thousand Pardons
I'm still trying to work out the refractive index of iron.
In the visible part of the spectrum, it ranges from about 2.3+2.6i to 2.9+3.2i.

6. Don't sound waves move faster in a stiffer medium? Density would be secondary. Darn, what's the word I want? Index of Boinginess?

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Originally Posted by mike alexander
Don't sound waves move faster in a stiffer medium? Density would be secondary. Darn, what's the word I want? Index of Boinginess?
Young's Modulus of Elasticity?

I must admit, I like Boinginess though

8. Ut
Established Member
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Feb 2004
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I would have done so much better in my EngPhys class if we used terms like Index of Boinginess...

9. Originally Posted by Ut
I would have done so much better in my EngPhys class if we used terms like Index of Boinginess...
Haha, yeah that does sound a bit more apt.

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Nov 2003
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Originally Posted by mike alexander
Don't sound waves move faster in a stiffer medium? Density would be secondary. Darn, what's the word I want? Index of Boinginess?
ROFL! Oh man, that's classic. I have a few friends who are structural engineers who will love that.

11. Just for kicks I Googled "Boinginess" and got 157 hits! Apparently musicians for one use the term; this is from some amp review:
The development team at Carvin has come up with the genuine article here. Lots of other manufacturers have jumped on the vintage bandwagon with startlingly varied results, but Carvin's Vintage 33, weighing in at a mere 44 pounds, is way more than just a packaging ploy--this amp is all-tube, with meticulous chassis assembly and traces, an innovative and smooth reverb that exhibits less "boinginess" than what we've grown to associate with Fender's hammond reverb tank, and a sonic character that ranges from brilliant clean tones to a growling-when-cranked overdrive channel.