Prismatic Section: Difference between revisions
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'''2-2- | '''urn:mrn:iala:dic:2-2-0020''' | ||
1. Cross-section of a prism by a plane normal to the refracting edge. The section is bounded by straight lines (usually three). | 1. Cross-section of a prism by a plane normal to the refracting edge. The section is bounded by straight lines (usually three). | ||
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2. In lighthouse practice, the term is also used for a cross-section of a transparent optical element bounded by three straight or slightly curved sides, approximating to a triangle, but of such shape that incident parallel rays of a particular wavelength are focussed after refraction or reflection (or both) by the section. | 2. In lighthouse practice, the term is also used for a cross-section of a transparent optical element bounded by three straight or slightly curved sides, approximating to a triangle, but of such shape that incident parallel rays of a particular wavelength are focussed after refraction or reflection (or both) by the section. | ||
[[Image:Ch2_Fig10.jpg|400px]] | [[Image:Ch2_Fig10.jpg|400px|border]] | ||
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Latest revision as of 09:33, 17 September 2026
1. Cross-section of a prism by a plane normal to the refracting edge. The section is bounded by straight lines (usually three).
2. In lighthouse practice, the term is also used for a cross-section of a transparent optical element bounded by three straight or slightly curved sides, approximating to a triangle, but of such shape that incident parallel rays of a particular wavelength are focussed after refraction or reflection (or both) by the section.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
