a plane through a focal point and normal to the axis of a lens, mirror, or other optical system.Compare principal plane.
the transverse plane in a telescope where the real image of a distant view is in focus.
Why are planes named after numbers, like the 747? Is there a 947 or a 658?After World War II, one of the largest aircraft manufacturers, Boeing, turned its attention from designing military craft to building commercial planes, along with missiles and spaceships. (Unrelated fact: when Boeing was forced to spin off its passenger flight division, the newly-formed company became United Airlines. Back to the late 1940s: Model numbers were assigned to each division of aircraft (from the Boeing website:) “300s …
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Origin of focal plane
First recorded in 1890–95
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
the plane that is perpendicular to the axis of a lens or mirror and passes through the focal point
the plane in a telescope, camera, or other optical instrument in which a real image is in focus
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012