Refracting angle of a prism

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(Opt.) the angle of a triangular prism included between the two sides through which the refracted beam passes in the decomposition of light.

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References in periodicals archive ?
Some species of the Molytinae possess a mucro, a secondary tooth located at the inner apical angle of the uncinate tibiae.
i) The shell elongation E is (as expected) monotonously increasing with the apical angle [alpha] and monotonously decreasing with the differential-growth index; the dependence of E upon the growth-dissymmetry index [delta] is less intuitive but is also monotonously positive.
Because of the irregularly coiled protoconch in the new genus, the width of the protoconch whorls, as well as the apical angle and spire angle could not be measured in the same way as in Avakubia.
strigipennis Moore in external morphology, but can be distinguished from it by the following features: the forewing has a brownish black line stretching from the apical angle to the outer side of inner margin; the oblique lines running from the apex of forewing to hindwing are more prominent; basal part of hindwing paler; the uncus wider, with 3 processes, middle one forked apically, and other 2 digitate; the gnathos has peg-like teeth; the valva shorter and broader; the harpe finger-shaped, sclerotized, broad at base, and with a minute apical hook; the aedeagus shorter, and with a crescent-shaped cornutus basally.
acuminata by the acuminate apex and tapering spire, but has a much smaller, shorter-spired shell with tighter coiled whorls and a less sharp apical angle.
Shell globose with rapidly expanding whorls; spire elevated: sutures not deeply impressed: aperture suboval to subrounded; thin inductura on parietal lip; ornament of short, prosocline lirae extending from suture on upper whorl surface; rest of surface smooth except for faint growth lines: apical angle 101 to 109 degrees.
Marginal impression distinct, narrow near apical angle, broadly widened to the basal angles.
Parameres short, rather flattened and truncate at apex, distal half subparallel with the inner apical angle directed mesad.
Genae dark brown; in posterior view, process of anal segment of male relatively short and broad, lobe-like, situated in middle of ventral margin; outer apical angle of genital styles not forked M.
Hindwing wider than forewing, brownish black, apical angle acute, outer margin oblique, fringe scales brown, area between costal margin and forewing grayish brown; Rs and [M.