Newton rings

The method is proposed by Hartl et al. [19-21]. The colorimetric interferometry technique, in which him thickness is obtained by color matching between the interferogram and color/fllm thickness dependence obtained from Newton rings for static contact, represents an improvement of conventional chromatic interferometry. 

Given a negative thin in the shadows place a ND film on top of the negative in the carrier. The film should be emulsion side down as base-to-base would increase the likelihood of Newton Rings. Increase the original print exposure slightly to compensate for the increased density. 

Topographic technique it is most suitable for small contact angles and is used in the study of black films of thickness 6-8 nm. This technique is based on the determination of the radii of the interference Newton rings when the film is observed in a reflected monochromatic light (Fig. 2.9). 

The applicability of the topographic technique can be extended by using of an approximated solution of Laplace equation. Here it is necessary to measure the radius n of the fc-th Newton ring of the meniscus surrounding the film, and thickness at which this ring emerges [70]. 

The microinterferometric method employed in the study of kinetics of foam film thinning allows to establish experimentally the liquids that form or do not form foam films. If a liquid possesses even small affinity to produce a foam, a circular film with clearly pronounced Newton rings is formed when it is drawn out of the biconcave drop. Films from aqueous surfactant solution can be obtained even at very small decrease in the surface tension (Act < 10 4 N m 1). It is sufficient to ensure a tension gradient between the film center and periphery. 

Upon the contact of a water drop with the flat water/soap solution in n-decane interface, a liquid hydrocarbon film was formed which is surrounded by Newton rings that may be seen in reflected light. Upon thinning, the film itself changes its color from white to grey and then to black. 

Differential interferometry in reflected light allows for the measurement of the shape of the upper reflecting snrface. This method was nsed by Nikolov et al. [253,273-275] to determine the contact angle, film, and line tension of foam films formed at the top of small bubbles floating at the surface of ionic and nonionic surfactant solntions. An alternative method is the holographic interferometry applied by Picard et al. [276,277] to study the properties of bilayer lipid membranes in solution. Film contact angles can also be determined from the Newton rings of liquid lenses, which spontaneously form in films from micellar surfactant solutions [217],... 

The experiments reported here make use of the Thin Film Colorimetric Interferometry technique for film thickness measurement. In this technique, 3 X 8 bit SXGA still pictures are after transformation from RGB to CIELAB colour space converted to the film thickness map using appropriate colour/film thickness calibration curves. They are obtained from Newton rings for static contact formed between the steel ball and the glass disc coated with the chromium layer only. During several last years the accuracy and resolution of TFCI has been improved and it is now able to measure film thickness to within 1 nm [13]. 

A vivid example of strips of equal thickness is Newton rings. They appear when a lens of a radius of curvature R lying on a carefully processed glass plate is irradiated with monochromatic light in the wavelength 1. Determine the radius of the mth ring. 

Find the radii of the second rj dark, and fifth light Newton rings in a monochromatic light /Iq= 0.56 pm provided the lens radius is / = 1.2 m. 

In the experiment with Newton rings, a liquid oil was poured between a lens and a sample stage table, with its refraction index less than that of glass. The radius of the eighth dark ring is = 2 mm X = 700 mn) whereas the radius R of the plane-convex lens is 1 m. Find the refraction index n of oil. 

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