Re: Sensors and Zooplankton

G'day Alan,

 >In order to see a greeblie that's 5cm long,
 >you need a wavelength of 10cm or
 >less, 2.5cm or less by choice. The speed
 >of sound in water is on the order of 1
 >km/sec, so a wavelength on the order of
 >1cm means a frequency on the order of
 >100 KHz. At these wavelengths, there is
 >essentially total absorbtion after a
 >few hundred metres.....
 >
 >And normal shrimp and other
 >zooplankton turn up beautifully on UHF
 >active sensors, but only within half a km.

Well like I said I'm not an engineer so I don't know if we've done 
something that breaks the laws of physics or what but the stuff we're 
looking at uses in excess of 150kHz to see it and its about 1.5 km
down.... 
so something doesn't gel here ;)

Cheers

Beth

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Elizabeth Fulton
c/o CSIRO Division of Marine Research
GPO Box 1538
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Phone (03) 6232 5018 International +61 3 6232 5018
Fax 03 6232 5053 International +61 3 6232 5053