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[[Image:Abbe-diagram 2.svg|right|thumb|380px|An Abbe diagram plots the Abbe number against refractive index for a range of different glasses (red dots). Glasses are classified using the Schott Glass letter-number code to reflect their composition and position on the diagram.]]
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[[Image:SpiderGraph Abbe Number-en.svg|250px|thumb|Influences of selected [[glass]] component additions on the Abbe number of a specific base glass.<ref>[http://glassproperties.com/abbe_number/ Abbe number calculation of glasses]</ref>]]
 
In [[physics]] and [[optics]], the '''Abbe number''', also known as the '''V-number''' or '''constringence''' of a [[Transparency (optics)|transparent]] material, is a measure of the material's [[dispersion (optics)|dispersion]] (variation of refractive index with wavelength) in relation to the [[refractive index]], with high values of ''V'' indicating low dispersion (low [[lens (optics)#Chromatic aberration|chromatic aberration]]). It is named after [[Ernst Abbe]] (1840–1905), the German physicist who defined it.
 
The Abbe number,<ref>{{cite book|last=Hovestadt|first=H.|title=Jena Glass and Its Scientific and Industrial Applications|year=1902|publisher=Macmillan and Co.|location=London|pages=1–81}}</ref><ref>{{cite book|last=Bergmann|first=Ludwig|title=Optics of Waves and Particles|year=1999|publisher=Walter de Gruyter|location=Berlin|isbn=3-11-014318-6|pages=198–201|coauthors=Clemens Schaefer}}</ref> ''V<sub>D</sub>'', of a material is defined as
 
:<math>V_D = \frac{ n_D - 1 }{ n_F - n_C },</math>
 
where ''n''<sub>D</sub>, ''n''<sub>F</sub> and ''n''<sub>C</sub> are the refractive indices of the material at the wavelengths of the [[Fraunhofer lines|Fraunhofer]] D-, F- and C- [[spectral line]]s (589.3 [[nanometre|nm]], 486.1&nbsp;nm and 656.3&nbsp;nm respectively).
 
Abbe numbers are used to classify [[glass]] and other optically transparent materials. For example, [[flint glass]] has ''V''&nbsp;<&nbsp;50 and [[crown glass (optics)|crown glass]] has ''V''&nbsp;>&nbsp;50. Typical values of ''V'' range from around 20 for very dense flint glass, around 30 for [[polycarbonate]] plastics, and up to 65 for very light crown glass, and up to 85 for [[fluorite|fluor]]-crown glass. Abbe numbers are only a useful measure of dispersion for visible light, and for other wavelengths, or for higher precision work, the [[dispersion (optics)|group velocity dispersion]] is used.
 
Due to the difficulty and inconvenience in producing sodium and hydrogen lines, alternate definitions of the Abbe number are used in some contexts ([[ISO]] 7944).<ref>{{cite web|last=Meister|first=Darryl|title=Understanding Reference Wavelengths|url=http://www.opticampus.com/files/memo_on_reference_wavelengths.pdf|publisher=Carl Zeiss Vision|accessdate=2013-03-13}}</ref>  The value ''V''<sub>d</sub> is given by
:<math> V_d = \frac{n_d-1}{ n_F - n_C }</math>
which defines the Abbe number with respect to the yellow Fraunhofer d (or D<sub>3</sub>) [[helium]] line at 587.5618&nbsp;nm wavelength. It can also be defined at the green [[mercury (element)|mercury]] E-line at 546.073&nbsp;nm:
:<math> V_e = \frac{n_e-1}{ n_{F'} - n_{C'}}</math>
where F' and C' are the blue and red [[cadmium]] lines at 480.0&nbsp;nm and 643.8&nbsp;nm, respectively.
 
An '''Abbe diagram''' is produced by plotting the Abbe number ''V''<sub>d</sub> of a material versus its refractive index ''n''<sub>d</sub>. Glasses can then be categorised by their composition and position on the diagram. This can be a letter-number code, as used in the [[Schott Glass]] catalogue, or a 6-digit [[glass code]].
 
Abbe numbers are used to calculate the necessary [[focal length]]s of [[achromatic lens|achromatic doublet]] [[lens (optics)|lenses]] to minimize [[chromatic aberration]].
 
The following table lists standard wavelengths at which n is usually determined, indicated by subscripts.<ref>L. D. Pye, V. D. Frechette, N. J. Kreidl: "Borate Glasses"; Plenum Press, New York, 1977</ref> For example, n<sub>D</sub> is measured at 589.3&nbsp;nm:
 
{| class="wikitable"
|-
! λ in nm
! [[Fraunhofer lines|Fraunhofer's symbol]]
! Light source
! Color
|-
| 365.01
| i
| Hg
| UV
|-
| 404.66
| h
| Hg
| violet
|-
| 435.84
| g
| Hg
| blue
|-
| 479.99
| F'
| Cd
| blue
|-
| 486.13
| F
| H
| blue
|-
| 546.07
| e
| Hg
| green
|-
| 587.56
| d
| He
| yellow
|-
| 589.3
| D
| Na
| yellow
|-
| 643.85
| C'
| Cd
| red
|-
| 656.27
| C
| H
| red
|-
| 706.52
| r
| He
| red
|-
| 768.2
| A'
| K
| IR
|-
| 852.11
| s
| Cs
| IR
|-
| 1013.98
| t
| Hg
| IR
|}
 
==See also==
*[[Abbe prism]]
*[[Abbe refractometer]]
*[[Calculation of glass properties]], including Abbe number
*[[Glass code]]
 
==References==
{{reflist}}
 
{{DEFAULTSORT:Abbe Number}}
[[Category:Dimensionless numbers]]
[[Category:Optics]]
[[Category:Glass physics]]

Revision as of 13:42, 5 March 2014

"Why does my computer keep freezing up?" I was asked by a lot of people the cause of their computer freeze issues. And I am fed up with spending much time inside answering the question time and time again. This post is to tell you the real cause of your PC Freezes.

So one day my computer suddenly started being weird. I was thus frustrated, considering my files were missing, and I cannot open the files which I required, plus then, suddenly, everything stopped functioning!

One of the many overlooked reasons a computer usually slow down is considering the registry has become corrupt. The registry is basically a computer's running program. Anytime you're running the computer, entries are being produced plus deleted from a registry. The impact this has is it leaves false entries inside your registry. So, the computer's resources must function about these false entries.

Registry products have been crafted for one purpose - to clean out the 'registry'. This is the central database which Windows relies on to function. Without this database, Windows wouldn't even exist. It's so significant, that a computer is frequently adding and updating the files inside it, even when you're browsing the Internet (like now). This is amazing, nevertheless the difficulties occur when some of those files become corrupt or lost. This happens a lot, and it takes a superior tool to fix it.

There are a great deal of regzooka s. Which 1 is the greatest is not simple to be determined. But if we like to stand out one amidst the multitude we must take into consideration several products. These are features, scanning speed time, total errors detected, total errors repaired, tech support, Boot time performance plus price. According to these goods Top Registry Cleaner for 2010 is RegCure.

The software finds these difficulties plus takes care of them in the shortest time possible. The hard drive would additionally result difficulties sometimes, particularly in the event you have one that is almost maxed. When a commence the machine, the are a lot of booting processes involved and having an almost full storage space refuses to help a bit. You will usually have a slow PC because there are numerous things inside the hard disk being processed simultaneously. The best method to resolve this problem is to upgrade. This allows your PC several time to breath and functioning faster swiftly.

Perfect Optimizer is a superior Registry Product, changes consistently plus has lots of qualities. Despite its price, there are which the update are really beneficial. They provide a lot of support via phone, send plus forums. We would wish To go and visit the free trial to check it out for yourself.

Often the best way is to read ratings on them plus if countless users remark about its efficiency, it is very likely to be work. The best piece is that there are numerous top registry products which work; we only have to take a choose.

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