Physics Help Forum Pressure/Density and Refractive Index of Air

 Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

 Apr 26th 2008, 12:28 PM #1 Junior Member   Join Date: Apr 2008 Posts: 4 Pressure/Density and Refractive Index of Air Does anyone know how the refractive index of air varies with compression? I know changes in refractive index due to temperature variation can be visible to the naked eye (for example, a mirage); I'm trying to figure out the minimum intensity of a sound wave in air for which the resulting variation in density (compression and rarefaction) produces enough change in the refractive index to make the sound wave visible to the naked eye. --Kevin C.
May 3rd 2008, 03:07 AM   #2
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 Originally Posted by TwistedOne151 Does anyone know how the refractive index of air varies with compression? I know changes in refractive index due to temperature variation can be visible to the naked eye (for example, a mirage); I'm trying to figure out the minimum intensity of a sound wave in air for which the resulting variation in density (compression and rarefaction) produces enough change in the refractive index to make the sound wave visible to the naked eye. --Kevin C.
I think what you're looking for is the Ciddor equation .....

These might also be good starting points:

http://mintaka.sdsu.edu/GF/explain/a.../air_refr.html

http://www.fs.wettzell.de/publ/dfpreport/node3.html

Here is a paper that might indirectly help:

http://www.cfa.harvard.edu/~jbattat/apollo/references/atmosphere/chambers_astrometryWithPanStarrsAndPS1_pushingTheL imitsOfAtmosphericRefraction_2005.pdf