White light water droplets

Light is scattered all around us— the fact that the sky above us appears blue, the clouds white, and the sunset shades of reds and oranges is a consequence of preferential scattering of light from air molecules, water droplets, and dust particles. This scattered light carries messages about the scattering objects. 

Figure 2.4 (Upper) White-light (polarized) photomicrograph, in reflected mode, of an suspension with a significant emulsified oil content. With polarized light, the clays (C) appear bright, but the oil droplets cannot be seen at all. (Lower) In this reflected-light photomicrograph, of the same field of view as above, the fluorescence mode shows bright oil droplets in a dark water-continuous phase. In this photograph the clays cannot be seen. From Mikula [66], Copyright 1992, American Chemical Society.

Figure 18. White-light (polarized) photomicrograph in reflected mode of an oil-in-water emulsion with a significant solids content. With polarized light, the clays (C) appear bright, but the oil droplets cannot be seen at all.

Figure 21. White-light (top) and blue-light fluorescence mode (bottom) photomicrographs of a water-in-oil emulsion. With white light the water droplets have internal reactions that lead to a halo effect and an incorrect size estimate. With incident blue—violet light to excite oil-phase fluorescence, the emulsified water droplets appear as dark circles in a bright oil background and are significantly easier to size. However, droplets that are above or below the plane of focus will still be incorrectly sized.

White light is actually made from a bundle of colored components, which together blend into a white color. A rainbow occurs when sunlight passes via droplets of water, which refract (change direction) and reflect the light, such that its colored components separate according to their different wavelengths and thereby... 

Figure 8. A digital image of water droplets on a colorful superhydrophobic surface composed of electrospun fibers on a glass slide. The picture was taken from a nearly normal direction with a white light source beneath the slide.

Milk is a very compKcated dispersed system (see Section 7.6.3.2.1) in which casein molecules form a micellar dispersion, globular whey proteins a colloidal dispersion, fat present in the form of fat droplets (mflk microsomes) forms an emulsion, particles of lipoproteins form a colloidal suspension and low molecular weight substances (lactose and other sugars, amino acids, minerals and water soluble vitamins) form true solutions. Milk s typical white colour is related to the scattering and absorption of light by the fat particles and casein micelles. The yellowish colour that is sometimes seen is caused by carotenoid compounds dissolved in the fat phase (cream and butter), while the greenish colour of whey is caused by riboflavin. 

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