For many years channel spectra, caused by multiple reflections of light between the faces of flat samples of optical material, have been used to determine refractive indices. Interferometers are excellent for this measurement, particularly in the far ir spectral region where their superior sensitivity and spectral resolution are required. The theory of the method is developed and the limitations are discussed. Experimentally determined refractive indices of silicon, germanium, and fused quartz are presented. These indices have been determined by these methods from data obtained with the Aerospace lamellar grating interferometer.

The differential scattering cross section for single carbon particles is measured in the visible. The data are mathematically inverted to obtain the complex index of refraction and particle radius.

Far ir Fabry-Perot type interference filters consisting of two parallel, closely spaced metal meshes have been reported by others. Using improved techniques, filters of this type have been fabricated with larger finesse and peak transmittance. Measured transmittance curves, obtained with the Aerospace lamellar grating interferometer have led to transmittance peaks whose sharpness appears to be limited principally by the beam convergence angle within the instrument (8 degrees ). From the measured peaks, finesses as large as 100 are obtained. Available mesh materials permit the construction of filters for any frequency from 10 cm(-1) (or lower) to at least 200 cm(-1). These will require absorbing components to eliminate unwanted harmonics.

The research in this paper quantifies the solar erythemal UV exposures to the skin through a common summer garment during outdoor activities. The

The research in this paper quantifies the solar erythemal UV exposures to the skin through a common summer garment during outdoor activities. The