 Solution

Features only a few tens of nanometres wide lie below the ordinary visible-light diffraction limit, approximately $\lambda /(2\mathrm{NA})$. The microscope cannot resolve individual rods, and unpolarized illumination does not directly reveal the orientation-dependent optical response. Scanning electron microscopy and atomic force microscopy can resolve the surface pattern. Transmission electron microscopy is another possible choice if a suitably thin specimen can be prepared.