# Pfund's method for refractive index

I wish to obtain the refractive index of a smooth surface using only a laser of given wavelength and a light sensor. I thought of using the Pfund method (attached), but I can't understand how the light sensor would fit in instead of the paper. I must use the sensor by the way. Can this be done on a horizontal table and then detected using a sensor?

http://www.lehigh.edu/imi/docs_edu/RefractiveIndexPfundsMethod.pdf