Abstract: The Brownian motion of polypropylene particles is studied by using a computer image acquisition system, which consists of a microscope, a CCD camera and a user interface. The pictures captured are further analyzed with a MATLAB program and the coordinates of Brownian particles are read out. Based on the statistics of a large sample of data, the Boltzmann constant is determined at a relative error of 4%. Moreover, the Gaussian distribution of the displacements of Brownian particles and the linear growth of its second moment with time are verified.

Key words: Brownian motion, Boltzmann constant, microscopic imaging system