Particle Counts in the Ultramicroscope


WHEN using the type of ultramicroscope designed by Prof. Whytlaw-Gray1 for the counting of particles in smoke and other aerosols, a stream of gas is passed intermittently through a glass cell of known dimensions, which is strongly illuminated. The number of particles which scatter light is noted each time the gas stream stops. The distribution of particle counts was found to follow a Poisson series very closely. Thus the number of times one would expect to find 0, 1, 2, 3... n particles in the field is given by where N is the total number of fields counted and x is the average number of particles per field2.

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  1. 1

    Whytlaw-Gray and Patterson, "Smoke" (Arnold, 1932).

  2. 2

    Badger and Dryden, Trans. Faraday Soc., 35, 607 (1939).

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BADGER, E. Particle Counts in the Ultramicroscope. Nature 157, 480 (1946) doi:10.1038/157480b0

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