Recording refractometer for measuring refractive indices of optical glasses over a wide range of wavelengths

A description is given of a spectrometer on which refractive indices of prismatic specimens have been measured from the near ultra-violet to the near infra-red. The relationships between accuracy of measurement and tolerance on angle measurement and wavelength are considered. Values of refractive index for six optical glasses are quoted for the wavelength range 366 mμ to 2300 mμ and with an estimated accuracy of ±0.00003 or better.