Page 205 - Algae

188 Algae: Anatomy, Biochemistry, and Biotechnology

TABLE 5.2
Refraction Index of Some Common Materials

Material Index
Vacuum 1.000
Air at STP 1.00029
Water at 08C 1.333
Water at 208C 1.332
Ice 1.309
Glycerin 1.473
Oil 1.466–1.535
Fluorite 1.434
Quartz 1.544
Glass, fused silica 1.459
Glass, Pyrex 1.474
Glass, Crown (common) 1.520
Glass, Flint 29% lead 1.569
Glass, Flint 55% lead 1.669
Glass, Flint 71% lead 1.805
Glass, Arsenic Trisulfide 2.040
Polypropylene 0.900
Polycarbonate 1.200
Plexiglas 1.488
Plastic 1.460–1.55
Nylon 1.530
Teflon 2.200
Salt 1.516

DIFFRACTION
Light waves change the progagation direction when they encounter an obstruction or edge, such as a
narrow aperture or slit (Figure 5.9). Diffraction depends on both wavelength of incoming radiation
(l) and obstruction or edge dimensions (a). It is negligible when a/l is sufficiently large, and
becomes more and more important when the ratio tends to zero. This effect is almost absent in

FIGURE 5.8 Dispersion of white light through a prism: the red portion of the spectrum deviates less than the
violet from the direction of propagation of white light.