[问答题]
A drop of oil on a pond appears bq gs,f px ,j (zn)ux*k5ptv;6iqktj27right at its edges, where its th(+htwxkag nz vg(uk*5. zc)w :ickness is much less than the wavelengths of visible light. What can yotcwxv)kza5n:w z.ghk(* ug+( u say about the index of refraction of the oil?
