glasses. 46. Opera glass.—In the old-fashioned opera glass, shownin diagram in figure 56, the erection of the image is providedfor by using a diverging lens for the eyepiece. This form oftelescope is quite short; for, in order that the eyepiece may 102 I.KiHT magnify the image, it is necessary that… … Figure 56verging waves strike the eyepiece, with their centers on ab.Therefore, in the formula or its equivalent -x + i = i u n v • f uf II .i must be taken as negative. Since f is also negative, becausethe lens is diverging, the numerator of the fraction in the lastequation is positive, and the…
Light
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