II. Medium refra&ivum cft, in quod radius luminis incidens nonrefta in fco-pum, fed fra&us alio reverberatur, tantoquc reftringitur amplius, quantomedium fuerit denfius, tanto minus,quanto mcdium fuerit rarius. III. Punclrum refrac~honis eftpundtum fupcrficiei corporis diaphani in quo…
Optics, Geometrical · Optical instruments
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