thumb|Refraction at interface
Most of the materials have a well-characterized refractive index, but these indices often depend strongly upon the frequency of light, causing optical dispersion. Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength (λ) of 589 nanometers.
There are also weaker dependencies on temperature, pressure/stress, etc., as well on precise material compositions (presence of dopants, etc.); for many materials and typical conditions, however, these variations are at the percent level or less. Thus, it's especially important to cite the source for an index measurement if precision is required.
In general, an index of refraction is a complex number with both a real and imaginary part, where the latter indicates the strength of absorption loss at a particular wavelength—thus, the imaginary part is sometimes called the extinction coefficient <math>k</math>. Such losses become particularly significant, for example, in metals at short (e.g. visible) wavelengths, and must be included in any description of the refractive index.
thumb|center|650px|Refraction, critical angle and total internal reflection of light at the interface between two media.
List
{| class="sortable wikitable"
|+ Some representative refractive indices
|- align=center
!Name of material||λ (nm)||data-sort-type=number|Refractive index no. n||Reference
|-
|Vacuum|| || 1 (by definition) ||
|-
|Air at STP|| ||1.000273||
|-
! colspan="4" |Gases at 0 °C and 1 atm
|-
|Helium||589.29||1.000036||
|-
|Carbon dioxide||589.29||1.00045||
|-
! colspan="4" |Liquids at 20 °C
|-
|Water||589.29||1.333||
|-
|Acetone|| ||1.36||
|-
|Ethanol (ethyl alcohol)||590.29||1.361||
|-
|60% glucose solution in water||589.29||1.4394||
|-
! colspan="4" | Solids at room temperature
|-
|Fused silica (a pure form of glass, also called fused quartz)||589.29||1.458||
|-
|Sodium chloride||589.29||1.544||
|-
|Amber||589.29||1.55||
|-
|Strontium titanate||589.29||2.41||
|-
|Diamond||589.29||2.417||
|-
|Silicon carbide (moissanite; 6H form)|| 589.29||2.65||
|-
! colspan="4" | Other materials
|-
|Liquid helium|| ||1.025||
|-
|Perfluorohexane (Fluorinert FC-72)|| ||1.251||
|-
|Water ice|| ||1.31||
|-
|TFE/PDD (Teflon AF)|| ||1.315||
|-
|Cryolite|| ||1.338||
|-
|Cytop|| ||1.34||
|-
|Polytetrafluoroethylene (Teflon)|| ||1.35–1.38||
|-
| Sugar solution, 25%|| ||1.3723||
|-
|Cornea (human)|| ||1.373/1.380/1.401 ||
|-
|Lens (human)|| ||1.386–1.406||
|-
|Liver (human)||964||1.369||
|-
|Intestinal mucosa (human)||964||1.329–1.338||
|-
|Ethylene tetrafluoroethylene (ETFE)|| ||1.403||
|-
|Sylgard 184 (polydimethylsiloxane)|| ||1.4118||
|-
| Sugar solution, 50%|| ||1.4200||
|-
|Pyrex (a borosilicate glass)|| ||1.470||
|-
|Vegetable oil|| ||1.47||
|-
|Glycerol|| ||1.4729||
|-
| Sugar solution, 75%|| ||1.4774||
|-
|Crown glass (pure)|| ||1.50–1.54||
|-
|PETg|| ||1.57||
|-
|Polyethylene terephthalate (PET)|| ||1.5750||
|-
|Polycarbonate|| 150 ||1.60||
|-
|Crown glass (impure)|| ||1.485–1.755||
|-
|Flint glass (pure)|| ||1.60–1.62||
|-
|Bromine|| ||1.661||
|-
|Flint glass (impure)|| ||1.523–1.925||
|-
|Sapphire|| ||1.762–1.778||
|-
|Boron nitride || ||2–2.14||
|-
|Cubic zirconia|| ||2.15–2.18||
|-
|Potassium niobate (KNbO<sub>3</sub>)|| ||2.28||
|-
|Zinc oxide||390||2.4||
|-
|Cinnabar (mercury sulfide)|| ||3.02|| Birefringent: n<sub>ω</sub> = 2.905 n<sub>ε</sub> = 3.256
|-
|Silicon ||1200 - 8500 ||3.42–3.48||
|-
|Gallium(III) phosphide|| ||3.5||
|-
|Gallium(III) arsenide|| ||3.927||
|-
|Germanium||3000 - 16000 ||4.05–4.1||
|}
See also
- Sellmeier equation
- Corrective lens#Ophthalmic material property tables
- Optical properties of water and ice
References
External links
- International Association for the Properties of Water and Steam
- Ioffe institute, Russian Federation
- Crystran, United Kingdom
- Jena University, Germany
- Hyperphysics list of refractive indices
- Luxpop: Index of refraction values and photonics calculations
- Kaye and Laby Online Provided by the National Physical Laboratory, UK