The size of a sphere can be unambiguously and quantitatively defined by its diameter. However, a typical material object is likely to be irregular in shape and non-spherical. The above quantitative definition of particle size cannot be applied to non-spherical particles. The size of contaminants and particles are usually described in microns, a metric unit of measure where one micron is one-millionth of a meter.
Different techniques of size determination have different sensitivity. Number based techniques are more sensitive towards smaller particles. Mass-based techniques are more sensitive towards larger particles.
- Sensitivity determined by scattering
- Maximum sensitivity at intermediate size
- Sensitivity depends on, refractive index, polarisation, dispersity etc