Measuring the particle size of reduced iron powder by microscope

The resolution of an optical microscope can reach 0.2 micron under ideal circumstances, which is related to the wavelength of the light source and the numerical aperture of the lens. However, in practical application, the particle size measurement range of an optical microscope is 0.8~150 micron, and then the particle size of a powder can only be observed and determined by means of electron microscopy.