From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


<> The
transmittance values are for the transmission of the light through the
glass, not including the entrance and exit losses.  Thus you do get values
above 99%.  I'll also note that the reflectance does vary but the 4% value
is the thumb at work here - if you use that value, you get almost exactly
on for glasses in the middle of the glass curve and you're not too far off
for glasses at the ends.  Remember that the reflectance occurs when you
change the refractive index (RI) and is 0 at a 0 change of RI.  Thus, a
cemented lens set with a cement that has approximately the RI midway
between the two lenses will have very little reflection in the middle of
the lens set - a reason why cemented lenses are so desirable for many. Bob
May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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