Transmission spectroscopy of a thin membrane
Paul Nachman · American Journal of Physics · 1993
A few-micron-thick nitrocellulose membrane stretched flat across an open frame (a ‘‘pellicle’’) has gently modulated passbands typically spaced by 20–60 nm across the visible and near-infrared. This makes it an attractive subject for an upper-division laboratory exercise. In our experiment, students determine the membrane’s thickness d and refractive index n from spectra recorded over a range of incidence angles. These spectra illustrate the classical textbook problem of transmission by a parallel plate and yield values of d and n with uncertainties less than 1%.