There Drebbel learned lens grinding and optics, with the construction of a magic lantern and a camera obscura.
2.
:I guess Feynman chose the sphere because a spherical lens is easy to grind ( nothing to do with theoretical physics, just the way lens grinding works ).
3.
The two later volumes contained chapters written by James Gilbert Baker, George Ellery Hale, George Willis Ritchey and others on topics ranging from lens grinding to monochromators to photoelectric photometry.
4.
Since lens grinding for eye glasses was developed by the early 15th century, an artist could have obtained a lens, set his subject in strong daylight and projected a traceable image on the canvas.
5.
Birns supplied the underwater lighting for the US Man-in-the-Sea program, and for Sea Labs I, II, and III . He also established a separate Birns & Sawyer lens grinding facility in Riverside County to make telephoto lenses for the US Air Force and Navy.
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