AbstractThe use of peak‐to‐background ratios has been suggested for the analysis of particles or rough surfaces as the peak‐to‐background ratio is assumed to be independent of geometry. The validity of this assumption is examined for flat specimens. It is shown that the peak‐to‐background ratio does not vary much with sample orientation but does vary with voltage, tending to a limit at high voltages. Methods of analysis using the peak‐to‐background ratio are proposed and the effects of fluorescenc