The properties of materials that are differentiated on the basis of direction dependency and direction independency classify isotropic and anisotropic.
Table of Contents
What is Isotropic?
The materials that possess such physical properties that remain identical in all directions of their crystalline structure are isotropic. In this type of material, the various material characteristics do not depend on the direction.
What is Anisotropic?
The materials having physical properties that vary with the change in the direction of the crystalline structure are anisotropic. Basically, in these materials, the characteristical behaviour shows dependency on the direction.
These are composed of unsymmetrical crystalline structures.
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Difference Between Isotropic and Anisotropic
The structure of the isotropic and anisotropic substances differs in the way of their atomic arrangement. This is so because, in isotropic material, the atomic arrangement shows uniformity as the atoms somewhat show an arrangement of slipping over one another. However, in anisotropic materials, the atomic arrangement is non-uniform, as the atoms exhibit distorted relations with each other.
The word ‘iso’ signifies ‘equal’ thus, isotropic materials exhibit identical properties in all the directions within the structure and hence are said to be direction independent. On the contrary, ‘aniso’ word means ‘unequal’, anisotropic materials possess non-identical properties in all directions as these tend to act differently in various directions, thus called direction-dependent.
The molecules within the structure of the isotropic materials show consistency in chemical bonding due to their structural arrangement. While the molecules within the structure of the anisotropic materials represent inconsistency in the chemical bonding due to non-uniform structure.
Isotropic materials are generally of darker appearance than anisotropic materials. This is because isotropic materials have a uniform structure. Thus, when the light passes from it is generally blocked from all directions. While anisotropic materials have non-uniform structures thus, it allows some amount of light to pass through their structure, thereby appearing lighter than the former.
Speed of light
In isotropic, the polarized light travels with the same speed in all directions within the structure, but as anisotropic materials are direction-dependent thus, the speed of polarized light varies with the change in the direction.
As no change in properties is noticed with the change in direction thus, the isotropic materials have only a single refractive index. As against, with the variation in direction, the properties also change thus, anisotropic materials have multiple refractive indices.
Isotropic materials do not show double refraction as when an unpolarized light passes through an isotropic medium; then, it never gets split into two. On the contrary, anisotropic materials show double refraction because here, the unpolarized light, when passes through the medium then it gets split into two.
Examples of isotropic materials are Glass, Diamond, Metal, Cubic crystals, etc. Whereas Wood, all crystals except cubic crystals, are considered an anisotropic material.
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Quick Comparison: Isotropic Vs Anisotropic
|Structure||It possesses uniformity in structure.||It possesses non-uniformity in structure.|
|Direction dependency||Not exist||Exist|
|Composition||Composed of Amorphous solids.||Composed of composite solids.|
|Properties||Exhibit Identical properties||Exhibit non-identical properties|
|Appearance||Material appearance is dark.||Material appearance is light.|
|Double refraction||These do not support double refraction||These support double refraction|
|Bond||Molecular bond is consistent.||Molecular bond is inconsistent.|
|Speed of light||Speed of light is same in all directions.||Speed of light is different in different directions.|
|Refractive index||Single refractive index||Multiple refractive indices|
|Example||Glass is the best example.||Wood is the best example.|
|Material||Lenses are made of isotropic material.||Wedges are made of anisotropic material.|
So, the difference in physical and mechanical properties of the materials due to the difference in the molecular orientation of the crystal mainly differentiates isotropic from anisotropic.