Page 8-9 isaac newton book

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a lot of when the celebrity manner, if ACBD (in

Fig. three ] reprefent a Glafs ſpherically gibbous on each each (uſually referred to as a Lens, ſuch as could be a could be a, or Spectacle glaſs, or AN Object glaſs of a Teleſcope) and or not it's needed to understand however lightweight falling upon it from any lucid purpose Q

ſhall be refracted, let Q M repreſent a Ray

falling upon any purpose M of its firſt ſpherical

Surface ACB, and by building a Perpendicular

to the Glaſs at the purpose M, notice the firſt re-

fracted Ray M N by the Proportion of the

Sines seventeen to eleven.

Let that Ray in going out of the Glaſs be incident upon N, and so notice

the ſecond refracted Ray weight unit by the Proporti-

on of the Sines eleven to seventeen.

And when the ſame manner might the Refraction be found once the

Lens is gibbous on one ſide and Plane or Con-

cave on the opposite, or bowl-shaped on each each.

A X. VI.

Homogeneal Rays that ensue feveral

Points of any Object, and fall sheer or almoſt sheer on any reflective or refract- ing Plane or ſpherical Surface, ſhall afterward diverge from ſo several alternative Points, or be Parallel to ſo several alternative Lines, or converge to ſo several alternative Points, either accurately or with none with none.

and therefore the and therefore the can happen, if the

Rays be mirrored or refracted ſucceſſively by 2 or 3 or additional Plane or Spherical Surfaces.

the purpose from that Rays diverge or to

which they converge could also be referred to as their Focus.

and therefore the focus of the incident Rays being gi-

ven, that of the mirrored or refracted ones might

be

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be found by finding the Refraction of any 2

Rays, as above; or additional promptly therefore.

Caf. 1. Let ACB [in Fig. 4.] be a reflective or

refracting Plane, and also the focus of the incident Rays, and letter of the alphabet letter of the alphabet C a perpendicular thereto Plane.

And if this perpendicular be made to nine,

ſo that letter of the alphabet C be capable QC, the purpose letter of the alphabet, fhall

be the main focus of the mirrored Rays. Or if qC

be taken on the ſame ſide of the Plane with

QC and in Proportion to a C because the sin of

Incidence to the sin of Refraction, the purpose the purpose be the main focus of the refracted Rays.

Caf.2. Let ACB [in Fig. 5.] be the reflective

Surface of any Sphere whoſe Center is E. Bi-

ſect any Radius therefrom (fuppofe EC) in T,

and if in this Radius on the ſame fide the purpose T you are taking the Points letter of the alphabet and letter of the alphabet, ſo that TO, TÉ, and T , be continual Proportionals, and also the purpose letter of the alphabet be the main focus of the incident Rays, the purpose letter of the alphabet ihall be the main focus of the mirrored ones.

Cal 3. Let ACB [in Fig. 6.] be the refracting

Surface of any Sphere whole Center is E. In

any Radius therefrom E C made each ways in which

take ET and Ct capable each other and fe-

verally in ſuch Proportion thereto Radius as

the leffer of the Sines of Incidence and Re-

fraction hath to the distinction of thoſe Sines.

And then if within the within the you discover any 2

Points letter of the alphabet and letter of the alphabet, ſo that TQ be to ET as Et

to t q, taking t letter of the alphabet the contrary manner from t that TQ lieth from T, and if the purpose letter of the alphabet be the main focus of any incident Rays, the purpose the purpose be the main focus of the refracted ones.

And

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