The response of a forward-scattering, laser optical` particle counter has been studied as a function of particle size, shape, and refractive index. Monodisperse aerosols of di-octyle phthalate (DOP), NaCl, and carbon black generated by the electrostatic-classification and vibrating-orifice methods and PSL particles were used. The results have been compared with theoretical, light scattering calculations and found to be in good agreement with the theoretical results.

For the transparent, spherical particles of PSL and DOP, the instrument response curve shows an oscillatory character due to resonant. effects in light scattering involving monochromatic light. For the nonspherical particles of NaCl the oscillatory character is less pronounced. For the light absorbing particles of carbon black and methylene blue, the instrument output is a smooth, monotonic function of particle size.

The loss of particle count by optical and electronic coincidence has also been studied . The experimental results are in good agreement with theoretical predictions.

Units: SI