The vertical energy flux density for the electromagnetic fields near the surface of a silver strip on a glass substrate is computed for an incident plane wave to aid in the measurement of the width of the strip. The dimensions of the strip cross section, e.g., 300 nm by 100 nm, are a fraction of the wavelength of the incident light , 632.8 nm. The flux 1 nm above the surface shows sharp spikes at the edges of the strip. The features of the fields near the surface could be used for accurate determination of the width of the strip by measurements up to about 30 nm above the strip. The effects of other variables are also shown in the figures.