Effect Of Oblique Incidence Research Articles

Ionospheric reflection processes for long radio waves—II

In a previous paper ( Westcott , 1962), the reflection process of very long waves within an ionospheric medium was considered. The Darwin-Hartree microscopic theory of re-radiation was used to derive formulae for 1. (i) the contribution by an elementary layer of a horizontally stratified ionosphere to the reflected field below the medium and 2. (ii) the integrated contribution to the reflected field due to a finite layer. These formulae were developed for a vertically incident wave and applied to an exponential isotropic ionosphere. In this paper the formulae are extended to determine the effect of oblique incidence on the reflection process and the results obtained are complementary to those obtained in the previous paper. For vertically polarized waves it is shown that the pole occurring at the level of zero refractive index in the full wave equations can seriously affect the reflection process at very low frequencies. As the wave frequency increases through the band 8–128 kc/s, with incidence at 60° it is shown that even when small collision frequencies are assumed the effect of the pole diminishes. The results then become very similar to those obtained for horizontally polarized waves where the main reflections occur from the level at which the Booker function q is zero.

Calculation of the Ion Optical Properties of Inhomogeneous Magnetic Sector Fields Part 3: Oblique Incidence and Exit at Curved Boundaries

In previous papers 1.2we presented the radial second order imaging properties of inhomogeneous magnetic sector fields with normal incidence and exit at plane boundaries. These fields may provide very high mass resolving power and mass dispersion without increase in radius or decrease of slit widths. In the present paper the calculations are extended to include the effect of oblique incidence and exit at curved boundaries. The influence of the fringing fields on axial focusing when the boundaries are oblique, is accounted for. It is shown that the second order angular aberration may Le eliminated by appropriate curvature of the boundaries.

The Effects of Collimation and Oblique Incidence in Length Interferometers. I.

An investigation has been made of the effects of position and size of diaphragm apertures on the interference fringes in length interferometry. The results indicate that, while the well-known correction formula for the effect of the oblique rays from a point source off the optic axis is always applicable, the effect of finite area of aperture is a more complex one and is not in general proportional to the length measured. This effect depends essentially on the phase differences arising from different points of the aperture and is oscillatory in character.

The Effects of Collimation and Oblique Incidence in Length Interferometers. II.

It is important in length determinations by interferometry to know the effect on the fringe pattern of an entrance aperture of finite size through which the light enters the interferometer. The correction generally applied has been found to be in error (Bruce 1955). This paper is a further discussion of this correction. Both two-beam and multiple-beam systems are discussed and show, in accordance with experiment, that the correction at present applied for the finite size of the aperture appears to be invalid.

The Effect of Oblique Incidence on the Conditions for Single Scattering of Electrons by Thin Foils

In setting up and applying criteria for the single scattering of electrons by thin foils, it has been usual to assume that the principal deviations from single scattering are caused by the combination of small deflections with one large one. It is here shown that with electrons obliquely incident on the foil much more serious deviations may be caused by the combination of two deflections of the same order of magnitude. It is concluded that the difference observed by Chase and Cox between the scattering at 90\ifmmode^\circ\else\textdegree\fi{} to the two sides of a foil on which electrons are incident at 45\ifmmode^\circ\else\textdegree\fi{} may be ascribed to this cause. The bearing of this factor on the negative result of Dymond's experiment on the polarization of electrons is also considered.