Elements of natural philosophy (Volume 2-3) . a com-bination of lenses placed close together; and Equation(32), the deviation at a single surface. § 38. The several terms of these Equations are the re-To find relativeciprocals of elements involved in the discussions which measures for the vergency ofare tO follow. The incident and pencil of light being Fig*21 deviated *»! small, the versed sine of half the arc DD\ has been disregard- ed, and the arc itself ~^| -^ may be regarded as . X^-^ Ea>s su^osed t0 coinciding with the x^^^^ diverge both . 1 t 1 11 ^e^jJK before and after tangent line
Elements of natural philosophy (Volume 2-3) . a com-bination of lenses placed close together; and Equation(32), the deviation at a single surface. § 38. The several terms of these Equations are the re-To find relativeciprocals of elements involved in the discussions which measures for the vergency ofare tO follow. The incident and pencil of light being Fig*21 deviated *»! small, the versed sine of half the arc DD\ has been disregard- ed, and the arc itself ~^| -^ may be regarded as . X^-^ Ea>s su^osed t0 coinciding with the x^^^^ diverge both . 1 t 1 11 ^e^jJK before and after tangent line at the ^^ \ deviation? and vertex 0, and as ar taken; naving been described about either of the points C, F\or F, as a centre, indifferently; and denoting the lengthof the arc 0 D by a, and the number of degrees in thisarc when referred to the centre F, corresponding to theradius f^ by w, we shall have the proportion, 2 at ./: 360° :?n; wThence, Number ofn op(\o 1 degrees in this 71 = * . JL arc referred to 2 tf f the centre F\. 19S NATURAL PHILOSOPHY. Number ofdegrees in samearc referred tothe centre F; in which * denotes the ratio of the diameter of a circleto its circumference. When this arc a is referred to the centre F\ corres-ponding to a radius f, its number of degrees, denotedby », becomes, , a . 360° 1n = —-, and dividing the first of these Equations by the second,we find, Eatio of theabove values; n 1 7T Conclusion for diverging rays. whence we conclude that — and — measure the relative f f divergence of the incident and deviated rays. When the devi-ated rays meetthe axis at F\ onthe opposite sideof the deviatingsurface from theradiant, the value/, being laid offin a contrary di-rection from the
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