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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]]

Latest revision as of 20:17, 17 September 2014

If you should speed up the PC then we have come to the right place. I will show we, now, five fast ways to drastically boost a computer's performance.

Most of the reliable businesses can offer a full money back guarantee. This signifies which you have the opportunity to get a cash back if you find the registry cleaning has not delivered what we expected.

With RegCure we can easily enhance the start and shut down of the computer. The program shows the scan progress plus we shouldn't worry where it happens to be working at that time. It shows you precisely what happens. Dynamic link library section of the registry may cause severe application failures. RegCure restores plus repairs the registry and keeps we from DLL. RegCure can create individual corrections, thus it could works for the demands.

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The registry reviver must come because standard with a back up plus restore center. This should be an effortless to implement process.That signifies which should you encounter a issue with your PC following utilizing a registry cleaning we can merely restore your settings.

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By restoring the state of the program to an earlier date, error 1721 may not appear inside Windows 7, Vista plus XP. There is a tool called System Restore which we have to use in this process.

If you wish To have a computer with quick running speed, you'd better install a advantageous registry cleaner to wash the useless files for we. As long as we take care of your computer, it might keep inside wise condition.

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