Difference between revisions of "Refraction"

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[[File:Csm GRIN-Linse b83f209974.jpg|noframe|300px|right|Gradient Index Lens]]
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[[File:Csm GRIN-Linse b83f209974.jpg|thumb|right|Gradient Index Lens]]
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==General Description==
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Refraction is the word used to [[describe]] the [[phenomenon]] of a <u>[[change]]</u> in direction that an electromagnetic wave travels in.<ref>https://www.dictionary.com/browse/refraction</ref>
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Refraction is the word used to [[describe]] the [[phenomenon]] of a <u>[[change]]</u> in direction that an electromagnetic wave travels in.<ref>https://www.dictionary.com/browse/refraction</ref> Electromagnetic radiation (which includes light) is observed to change direction when it's velocity changes. How much this velocity differs from the velocity in a vacuum is commonly called the refractive index. The vacuum value is set to 1 for all wavelengths of electromagnetic radiation.
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==Introduction==
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Electromagnetic radiation (which includes light) is observed to change direction when it's velocity changes. How much this velocity differs from the velocity in a vacuum is commonly called the [[refractive index]]. The vacuum value is set to 1 for all wavelengths of electromagnetic radiation.<ref name= "Snell">Refraction, Snell's law, and total internal reflection; http://buphy.bu.edu/py106/notes/Refraction.html</ref>
  
  
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==Mechanisms of Refraction==
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==Beginner==
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[[File:Wave Refraction Example small.gif|frame|right|Wave Refraction Example]]
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<Youtube>https://www.youtube.com/watch?v=wlcsSdsJG6I</Youtube>
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==Advanced==
  
 
It is commonly believed that the absolute value of the refractive index is what causes electromagnetic radiation to bend. This is an incorrect view.
 
It is commonly believed that the absolute value of the refractive index is what causes electromagnetic radiation to bend. This is an incorrect view.
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The change of direction of electromagnetic radiation occurs when an [[absolute refractive index]] along an  [[arbitrary]] path of travel <u>changes</u>.
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The change of direction of electromagnetic radiation occurs when the [[absolute refractive index]] along an  [[arbitrary]] path of travel <u>'''changes'''</u>.<ref name= "Snell">Refraction, Snell's law, and total internal reflection; http://buphy.bu.edu/py106/notes/Refraction.html</ref>
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'''Standard Physics Models of Refraction'''
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<u>''The two-medium model''</u>
  
 
The magnitude of change in the direction of the electromagnetic radiation is related to the magnitude of the difference in refractive indexes.
 
The magnitude of change in the direction of the electromagnetic radiation is related to the magnitude of the difference in refractive indexes.
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This can be modeled as a discrete boundary ([[Snell's Law]]). In this case, the [[relative refractive index]] values at the boundary determine the change in direction. The standard usage of this model is when the medium has a well-defined [[boundary]] between two [[isotropic]] [[homogenous]] mediums.
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This can be modeled as a discrete boundary ([[Snell's Law]]). In this case, the [[relative refractive index]] values at the boundary determine the change in direction. The standard usage of this model is when the medium has a well-defined [[boundary]] between two [[isotropic]] [[homogenous]] mediums.</u>.<ref name= "Snell">Refraction, Snell's law, and total internal reflection; http://buphy.bu.edu/py106/notes/Refraction.html</ref>
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The magnitude of the refractive index of a medium also has a wavelength dependence. <ref>Wavelength and the Index of Refraction; https://www.rpi.edu/dept/phys/Dept2/APPhys1/optics/review.html </ref>
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''Representation of a Two Medium Medium Model''
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[[File:Refr-diag-planesurf.jpg|thumb|left|Example diagram]]
 
[[File:Refr-diag-planesurf.jpg|thumb|left|Example diagram]]
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<br clear=all>  
 
<br clear=all>  
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<u>''Gradient Index Medium Model''</u>
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Refraction can also be modeled as a continuum according to Fermat's [[principle of least time]]. This method is necessary to model the path of electromagnetic radiation through certain types of mediums. The conditions for usage would be for mediums that have one or more of these properties: ill-defined [[boundaries]], are [[inhomogeneous]], are [[anisotropic]]. A medium with these properties is known as a [[Gradient Index Medium]].<ref>Gradient Index Optics
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By Erich Merchand; https://books.google.com/books?hl=en&lr=&id=pIrprJ0u2f8C&oi=fnd&pg=PP1#v=onepage&q&f=false</ref>
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''Representation of a Gradient Index Medium Model''
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[[File:Fitcurve.png|frame|right|Example Curve Fit to multi-layer]]
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[[File:Twolayer.png|frame|left|Example Two Layer Refraction]] [[File:Multilayer.png|thumb|center|Example multi-layer reraction]]
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<br clear=all>
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==Expert==
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The models for refraction in the previous section can be used to make approximately correct optical path predictions within a limited range of idealized physical situations.
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The fact is there are many more models of refraction.
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<Youtube>https://www.youtube.com/watch?v=XwgXFVWYDGw</Youtube>
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==See also==
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[[Terrestrial refraction]]
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Refraction can also be modeled as a continuum according to Fermat's [[principle of least time]]. This method is necessary to model the path of electromagnetic radiation through certain types of mediums. The conditions for usage would be for mediums that have ill-defined [[boundaries]], are [[inhomogeneous]] or are [[anisotropic]].
 
  
 
==References==
 
==References==

Latest revision as of 04:08, 23 April 2020

Gradient Index Lens

Refraction is the word used to describe the phenomenon of a change in direction that an electromagnetic wave travels in.[1]


Introduction

Electromagnetic radiation (which includes light) is observed to change direction when it's velocity changes. How much this velocity differs from the velocity in a vacuum is commonly called the refractive index. The vacuum value is set to 1 for all wavelengths of electromagnetic radiation.[2]


This property of a medium has a few different names.

NAME
Index of Refraction
Refractive Index
Optical Density
Relative permittivity and permeability

Beginner

Wave Refraction Example

Advanced

It is commonly believed that the absolute value of the refractive index is what causes electromagnetic radiation to bend. This is an incorrect view. The change of direction of electromagnetic radiation occurs when the absolute refractive index along an arbitrary path of travel changes.[2]

Standard Physics Models of Refraction

The two-medium model

The magnitude of change in the direction of the electromagnetic radiation is related to the magnitude of the difference in refractive indexes. This can be modeled as a discrete boundary (Snell's Law). In this case, the relative refractive index values at the boundary determine the change in direction. The standard usage of this model is when the medium has a well-defined boundary between two isotropic homogenous mediums..[2]

The magnitude of the refractive index of a medium also has a wavelength dependence. [3]


Representation of a Two Medium Medium Model


Example diagram
INFOGRAPHIC ABSOLUTE AND RELATIVE RI
Well-Defined Boundary


Gradient Index Medium Model

Refraction can also be modeled as a continuum according to Fermat's principle of least time. This method is necessary to model the path of electromagnetic radiation through certain types of mediums. The conditions for usage would be for mediums that have one or more of these properties: ill-defined boundaries, are inhomogeneous, are anisotropic. A medium with these properties is known as a Gradient Index Medium.[4]


Representation of a Gradient Index Medium Model


Example Curve Fit to multi-layer
Example Two Layer Refraction
Example multi-layer reraction



Expert

The models for refraction in the previous section can be used to make approximately correct optical path predictions within a limited range of idealized physical situations. The fact is there are many more models of refraction.


See also

Terrestrial refraction



References

  1. ↑ https://www.dictionary.com/browse/refraction
  2. ↑ 2.0 2.1 2.2 Refraction, Snell's law, and total internal reflection; http://buphy.bu.edu/py106/notes/Refraction.html
  3. ↑ Wavelength and the Index of Refraction; https://www.rpi.edu/dept/phys/Dept2/APPhys1/optics/review.html
  4. ↑ Gradient Index Optics By Erich Merchand; https://books.google.com/books?hl=en&lr=&id=pIrprJ0u2f8C&oi=fnd&pg=PP1#v=onepage&q&f=false
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