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kelly
2004-Dec-18, 06:15 AM
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? :o

Tensor
2004-Dec-18, 07:16 AM
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? :o

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.

A Thousand Pardons
2004-Dec-18, 02:16 PM
The speed of sound (http://hyperphysics.phy-astr.gsu.edu/hbase/tables/soundv.html) varies in different media, about 300 m/s in air (http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe3.html), 1500 m/s in water (http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe2.html), and 5000 m/s in iron. I'm still trying to work out the refractive index of iron. :)

Squink
2004-Dec-18, 02:59 PM
Scubastronomy? :lol:

Grey
2004-Dec-19, 04:48 AM
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.

mike alexander
2004-Dec-19, 08:50 AM
Don't sound waves move faster in a stiffer medium? Density would be secondary. Darn, what's the word I want? Index of Boinginess?

frogesque
2004-Dec-19, 12:44 PM
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 :lol:

Ut
2004-Dec-19, 02:17 PM
I would have done so much better in my EngPhys class if we used terms like Index of Boinginess...

Normandy6644
2004-Dec-19, 05:09 PM
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. :D

beck0311
2004-Dec-19, 08:27 PM
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. :lol:

Swift
2004-Dec-20, 03:01 PM
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.