Interference of light

Figure 10.10 Interference of light rays scattered by segments j and k in a polymer chain. Destructive interference increases with increasing 6.

Figure 10.11 Definition of variables required to describe interference of light scattered from points O and P.

The thickness of a film influences the interference of light waves reflected from the front and back of the film, and hence the reflectance. The thickness of an absorbing film can, therefore, be measured only as long as there is still a contribution of from the back of the film to the reflectance of the sample. Typical measurable thicknesses of metallic layers are <50 nm. 

Interference Films thin transparent films which exhibit colours by interference of light in the visible range. 

Figure 1. Layout of a generic spectrograph employing a reflection grating. Angles a and (3 have the same sign if they are on the same side of the grating normal. Inset the condition for interference of light by a diffraction grating.

Fig. 44.—Interference of light scattered by different parts of a polymer chain comparable in dimension with the wavelength.

Figure 12,4.1 The multiple reflection of light from microscopic oxide layers of different dimensions leads to constructive and destructive interference of light waves, producing a particular color effect. Different thicknesses reflect different colors.

FIG. 5.8 Interference of light rays scattered by segments i and j in a polymer chain. (Redrawn with permission of P. C. Hiemenz, Polymer Chemistry The Basic Concepts, Marcel Dekker, New York, 1984.)... 

The simplest filter is colored glass, which absorbs a broad portion of the spectrum and transmits other portions. Table 18-1 showed the relation between absorbed and transmitted colors. For finer control, interference filters are constructed to pass radiation in the region of interest and reflect other wavelengths (Figure 20-10). These devices derive their performance from constructive or destructive interference of light waves within the filter. 

Unlike colour filters, interference filters and gratings can lead to some optical artefacts of which all workers in this field should be aware. All processes of interference of light waves depend on the difference in optical path between the beams, as illustrated in Figure 7.7. The general law for constructive interference is then... 

IRIDESCENCE. The exhibition of tlte colors of the rainbow, commonly by interference of light of the various wavelengths reflected front superficial layers in the surface of a substance. 

Between the time a liquid film is first formed, until it thins to an equilibrium black film, the thickness can be measured by techniques based on the interference of light. For monochromatic light, the intensity of light, IR, reflected at angle 8 from a fluid film compared to the maximum intensity yielded by constructive interference, I0, enables the determination of the film thickness, t, as ... 

The interference of light waves can be easily demonstrated using a two-slit experiment (Figure 7.15). Monochromatic (sin-... 

During the nineteenth century a great variety of experiments on interference of light waves was devised, and the wave lengths of all sorts of light were very exactly measured. It was found that light always behaves exactly in accordance with the wave theory in such experiments, and this theory came to... 

Structural colors may be caused by the diffraction or interference of light by tiny, regularly-spaced structures within a substance. Many insects and bird feathers display structural color. Structural defects in a material s crystal lattice can also affect its color. Excess or missing ions act as color centers and may affect the way the substance absorbs light. 

Mica particles coated with a metal oxide film have three layers with different refractive indices (layer 1 and 3 are identical, layer 2 is mica) and four interfaces (see chapter 16.2). Interference of light is generated by reflections of all six possible combinations of the four interfaces. Some of them lead to equal effects. The thickness of the mica platelets varies according to a statistical distribution. As a con-... 

---