Measurement of gradient index profiles by Babinet fringe analysis.
A theory for determining one-dimensional ray deflections with the help of distorted Babinet fringes has been developed. An approach for investigating two-dimensional ray deflections has been presented. Applications of the techniques for the study of gradient index glass have been described.
The Birefringent Filter
Optical birefringent filters, which depend for their action on the interference of polarized light, can be designed to transmit very sharp bands (down to a fraction of an angstrom in width). The elementary theory necessary for their design is given.Three forms of wide field filters designed by Lyot are described in detail. A more recently developed split element, wide field filter requires only half as many polarizers as the earlier types, which may be an advantage for some applications.Various methods of adjusting the transmission bands of a birefringent filter, including the use of elements of variable thickness, and phase shifters are discussed. For most purposes the electro-optical phase shifters are probably the most promising. For special purposes, such as spectrophotometry, phase shifters composed of rotating fractional wave plates may be more advantageous. Two such phase shifters and their application, in simple and split element filters are described.A few crystalline materials which have been used or might be used to advantage in birefringent filters are mentioned.Finally, the possibility of using polarizing interferometers in combination with birefringent elements for filters with extremely sharp transmission bands (in the range of hundredths or thousandths of an angstrom) is very briefly discussed.
On the theory of extraction from falling droplets II
The theory of extraction of a substance, dissolved in droplets of a fluid, when these are falling (or rising) in an other fluid under the influence of gravity, is specialized for the case that the rate of falling (or rising) is very small. A perturbation method, well-known from quantum mechanics, is applied to determine the time of diffusion in second approximation.