Interference rings

These investigations agree well with experiments by Trillat [129] who found that the X-ray diagram of colloidal nitrocellulose showing a non-oriented structure of crystallites (interference rings), altered after being stretched to indicate a fibrous structure in which the crystallites were oriented along the axis in the direction in which the film was stretched. 

Hess et al. [25, 8] carried out X-ray investigations of nitrocellulose during the stabilization process. In the X-ray diagrams of the nitrocotton fibres immediately after nitration, almost no interference rings were visible. They appear... 

Electrodeposited binary alloys may or may not be the same in phase structure as those formed metallurgically. By way of illustration, we note that in the case of brass (Cu-Zn alloy), X-ray examination reveals that, apart from the superstructure of /3-brass, virtually, the same phases occur in the alloys deposited electrolytically as formed in the melt. Phase limits closely agree with those in the bulk. Debye-Scherrer interference rings indicate the presence of a strong distortion of the lattice, particularly in the a-phase brass. Electrodeposited a-brass, for instance, is... 

The distance between the Newton interference rings is measured precisely from the film photographs by means of a photometer. Knowing the film thickness, the contact angle is calculated from Eq. (2.6) [68]... 

Figure 14 Schematic of thin-film technique. The geometry of the oil film separating two water droplets (a) is recreated in a special holder in the thin-film measuring cell (b) (c) shows microscopic image at the beginning of the film-thinning process showing Newton interference rings.

This distance of 3-4.5 A which corresponds to the lattice forces in molecular lattices, may, through its frequent occurrence, account for the fact that interference it produces is especially intense. Thus, for example, in the fatty acids the reflections are especially intense in those planes which contain the chains and, consequently, have the same interplanar distance that also separates the individual chains and corresponds to the lattice forces. In liquids also, where, it is true, the oriented lattice coherence is lost but where the average distances of the molecules are determined by van der Waals cohesion forces, we find very frequently indistinct interference rings when these are interpreted, they show that a lattice plane distance of about 4 A prevails in the liquid also, at least, statistically. From the x-ray diagrams of hydrocarbons, e.g. of liquid isoprene, an average molecular distance of about 4 A can be calculated from the ring. 

The principal experimental result consists of the fact that in liquid crystals the blurred interference rings of which we have learned in the discussion of normal liquids split up in the magnetic field into a pair of crescents, whereas in the amorphous phase the influence of the magnetic field is inappreciable. Diagrams, which show this effect on exposure of the allyl ester of phenetol azoxybenzoic acid in the magnetic field have been taken by Hermann and Krummacher with Cu radiation a very definite accumulation of the interference intensity in the region of the equator is evident. 

Fig. 4.41. The interference ring system of the transmitted intensity may be regarded as wavelength-selective imaging of corresponding ring areas of an extended light source...

The radius pm of the mth-order interference ring is obtained from (4.73),... 

Fig. 4.68a,b. Measuring interference ring diameters with a linear diode array (a) correct alignment (b) misaligned diode array... 

As a consequence of the coherence, the laser light can be transmitted as an almost parallel bundle. The small divergence is a consequence of the unavoidable influence of diffraction. For radiation in phase and with the same amplitude over a circular aperture of diameter d, the angle 6 between the centre of the diffraction pattern and the first dark interference ring is given by... 

Biaxial materials display two melatopes (Figure 5.13c) and a far more complex pattern of interference rings. ... 

Light from the counter-electrode interferes with the light reflected from the membrane, giving an interference ring each time the optical path length changes by half a wavelength ... 

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