The kubelka-monk theory makes a relation between specular reflection and diffuse reflection of light by an equation.
Specular reflection: We know when light comes on any surface an amount of light is absorbed by material & amount of light is reflected by material
When light is reflected in any specific angle, for example, light reflected at a specific angle or direction at 80% and others different angle light is reflected at 20 %. Then it will be the specular reflection of light.
Diffuse reflection: when a light is reflected in a different angle, for example, light is reflected in different angle or direction at 80 % and specific angle reflection is 20%. Then it will be the diffuse reflection of light.
If materials specular reflection light is K & Scattering reflection light is S,
Here, R is reflection of light by material
If we get the reflection of light by material than we also find out the K/S value of material by maintaining this equation.
In spectrophotometer when we put the sample than a light source is applying on the sample and spectrophotometer find out the specular reflection and scattering reflection of material.
Importance of K/s value for Textile Dyes
Textile dyes produce different types of color. The light source which exists (400nm-700nm) is seen by Human eye and it describes as color.
When a light source is reflected by a material and reached on human eye than he or see color. If a textile material contains the good quality of dyes than it maintains specular reflection more than Diffuse reflection.
The more specular reflected light is seen by human eye than it will be good color produced by the dye. And we can say that the strength of dye is good.
This states that the absorbance of light energy of a specific wavelength by an absorbing medium varies directly with the thickness of absorbing medium (also called optical path) and also varies directly with the concentration of the absorbing material.
Components of spectrophotometer
In UV/Vis spectrophotometer when we put the dye-liquor sample in cuvette a light source Po goes through the dye-liquor solution. An amount of light is absorbed by the solution and the light source after absorbed by dye liquor solution will be P
Then, Transmittance, T= P/P0
% Transmittance, % T= 100T
And, Absorbance= Log10 Po/P
Here, A is absorbance, e is molar absorptivity, b is path length of the sample, C is the concentration of the compound in solution.
Importance of Beers-lambert law for Textile Dyes
Textile dyes maintain a bond between dyes-fiber interactions. Good quality of dyes maintains dyes-fiber interaction more than other dyes. By Beers-lambert law in UV-Vis Spectrophotometer we can measure the strength of dye.
For measure the strength of dye, We need to take the Dye-liquor solution after dyeing. For putting this solution in spectrophotometer we get the Transmittance or absorbance value of light by the dye-liquor solution.
If the absorbance of light by the dye-liquor solution is more than the strength of dye is not good and the dye is also harmful to the environment.