Physical principals and the relations between Surface Plasmon Resonance (SPR) spectra and geometrical properties of metal nanostructures specially silver and gold were reported. Applying SPR technique enable us to investigate the accuracy of some simple equations for investigating geometrical properties of metal nanostructures based on their plasmonic spectrum. Geometrical properties, shape and size polydispersity of particles as well as particles’ embedding medium refractive index are the crucial ignored parameters, effective in the accuracy of those equations. The restrictions of these relations in terms of shape, size distribution and refractive index of particles’ embedding medium are also investigated and compared with other published reports. Furthermore, the equations of spherical particles have been extended to non-spherical ones and their accuracy has been investigated. It was found that the modified forms of the equations may lead to more exact results for non-spherical metal particles.
