I would like to determine the thickness of a liquid film floating (uniformly/non-uniformly) on another immiscible liquid. How to photograph the cross section of the film (in a non-invasive manner) taking into account the curvature of the film at the edges of the surface of the container in which the experiment is being carried out.
I assume one simple way of doing it is to divide the measured surface area with the weight of the liquid added
Thickness=(Wt. of liquid added to the surface)/(Surface area of the container, assuming uniform distribution)
This is a crude method and it will not give the actual picture with respect to surface tension and viscosity of the liquids and their interfacial properties.
I am not sure, but you may try to measure the thickness using a refractometer. If there is a reflection from both surfaces, film surface and the liquid surface, there must be an interference peak. From this, you can measure the thickness d.
constructive interference follow this equation
mλ = 2 d
For two successive interference peaks, two widely spaced maxima or minima can be examined and the number of fringes in between are counted. Hence two equations are generated;
m1λ1=2d
m2λ2=2d
Where m1 and m2 are the integer values of the edge maxima or minima (note because this is the integer number of wavelengths in the path difference m1>m2) and λ1 and λ2 are the wavelengths (λ1
Тhe thickness of films is determinated with help of ellipsometry.
Thank you Shakhawan Al-Zangana and Lev Aleksandr Blagonravov for the reply.
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