In this paper we present our study of fluctuations of intensity of light scattered by particles of smoke plumes occurring in the atmosphere due to mixing of particles by large scale turbulent eddies. To do this we have calculated the mean intensity, relative variance, and temporal scale of fluctuations of intensity of scattered radiation in the focal plane of a receiving telescope. The results obtained enable a priori choice of the exposure time to be done for taking optical images of smoke plumes with a desired degree of averaging.