A representative value of the FWHM of this curve is 0.542 μm±0.05 μm; the uncertainty for a single measurement here being solely the resolution of the micrometer. This was substituted into Eq. (11) to obtain the refractive index of water. The measured refractive index of the water sample, nw, using this method is 1.35±0.01; the error being determined by choosing maximum and minimum values of the parameters with their associated errors. The same procedure was repeated a number of times in order to determine the precision (standard deviation) which was found to be ±0.1. A high standard deviation occurred because of the difference in the FWHM of each data set, which was a result of only having seven data points for each curve using the micrometer available.