Refractive index and thickness of a transparent ¯lm (ZnS) on a transparent substrate (BK-7 glass)
have been determined from measurement of normal incidence transmittance, using di®erent
methods. Some of the methods considered here are most widely used, as is apparent from the
literature. The outcome of this study could help a researcher in selecting an appropriate method for
such an application. The values of the refractive indices determined by di®erent methods were found
to be close to each other (within 0.5%). However, large (up to 4.4%) di®erences existed in the values
of the thickness determined by di®erent methods.