A fixed path ultrasonic interferometer for use in vapors is described, in which the stationary wave system between the quartz source and the reflector is explored by a traveling hot-wire. The hot-wire is calibrated for its change of resistance in terms of velocity-amplitude in the ultrasonic wave system. A correction is made for diffraction of the ultrasonic beam. In this apparatus wavelength and absorption measurements are made in ether, ethylene, benzene, carbon disulphide, and acetaldehyde vapors. All show an absorption considerably greater than the theoretical values based on the Stokes-Kirchhoff equations.

The point spread function of an optical system (PSF) with asymmetric apodization has been found possess a so-called 'good side' and a 'bad side'. The good side has decreased side-lobes whereas the bad-side shows increased side-lobes. This has been observed when the aperture is divided into three parts viz., two regions with apodizers and a central region as a transparent one. The asymmetry in the PSF has been found to increase with the width of the edge-strips and is seen to decrease with an increased apodization of the central region.

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