= 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. \b[<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.
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