Elements of natural philosophy (Volume 2-3) (1850)
Bartlett, W. H. C. (William Holms Chambers), 1804-1893 · New York : Barnes · leaf 213
we shall have, Equation fordiscussion; / // F.. + f n (40) Fig. 27. For -__ > —, or / > Fit, f will be negative, and Fu f the vergency ofthe deviated Keal radiants rayS w[\l \)q ne-between . rp, principal focus g^tlVe. liiat and infinity; is to Say, if a wave proceedfrom a point Give real… … .bor ^ —, or ii f<Fu,f will be positive, and the ver- Beai radiants gency of the deviated Avitliin the ipai focus; ra.Ys W1^ be positive.That is, if the wave pro-ceed from a point infront and situated be- prmcij Fig. 28.
Mechanics · Acoustics · Optics
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