[填空题]
The wings of a certain beetleld(i1 gwn0ug0rf-xr ( have a sx1dv eah3ro wa :.s:q3eries of parallel lines across them. When normally incident 460-nm ligewd:3sxavohr3a q. :1ht is reflected from the wing, the wing appears bright when viewed at an angle of 51$^{\circ}\,$. How far apart are the lines? nm
