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Brownian movement |
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Brownian movement or motion, zigzag, irregular motion exhibited by minute particles of matter when suspended in a fluid. The effect has been observed in all types of colloidal suspensions (see colloid colloid (kŏl`oid) [Gr.,=gluelike], a mixture in which one substance is divided into minute particles (called colloidal particles) and ..... Click the link for more information. )—solid-in-liquid, liquid-in-liquid, gas-in-liquid, solid-in-gas, and liquid-in-gas. It is named for the botanist Robert Brown who observed (1827) the movement of plant spores floating in water. The effect, being independent of all external factors, is ascribed to the thermal motion of the molecules of the fluid. These molecules are in constant irregular motion with a velocity proportional to the square root of the temperature. Small particles of matter suspended in the fluid are buffeted about by the molecules of the fluid. Brownian motion is observed for particles about 0.001 mm in diameter; these are small enough to share in the thermal motion, yet large enough to be seen with a microscope or ultramicroscope. The first satisfactory theoretical treatment of Brownian motion was made by Albert Einstein in 1905. Jean Perrin made a quantitative experimental study of the dependence of Brownian motion on temperature and particle size that provided verification for Einstein's mathematical formulation. Perrin's work is regarded as one of the most direct verifications of the kinetic-molecular theory of gases kinetic-molecular theory of gases, physical theory that explains the behavior of gases on the basis of the following assumptions: (1) Any gas is composed of a very large number of very tiny particles called molecules; (2) The molecules are very far apart compared to ..... Click the link for more information. . |
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You click on the red one and out scrambles the word 'portfolio'--which you notice is repeated in a row across the bottom before the word zooms out at you and the screen is changed to some monochrome spherical blobs of different sizes doing a dreamy Brownian movement around the screen. 15) where energy is not only dissipated at an interface, but also on its vicinity, coupled with a generalized theory of diffusion, allows one to evaluate the mechanism of transfer of this momentum throughout the sample fractal interfaces via a fractionary Brownian movement. If you just showed it at a student lecture and said, 'This is what Brownian movement looks like through a modern microscope,' nobody would even stop to question the fact. |
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