Determination of size and number density of water droplets by the measurement of intensity of scattered light

The concentration of water vapour varies with space and time. It is removed from the troposphere due the precipitation of water. The size of condensing nuclei and aerosol particles present in the atmosphere are comparable to the wavelength of visible radiation. According to Mie theory, the scattering properties are the function of size parameter x, refractive index m and the angle of scattering θ. The light scattered from condensing droplets illuminated by a 5 mw He-Ne laser beam is detected at 45° and 135° simultaneously. The observed ratio of intensities of scattered light is compared with the theoretically calculated value. The method also enables one to determine the number density N and modal size x_m of water droplets. The effect of ions of water vapour condensation is also studied by this method