Page 10-11 Isaac Newton Book

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And by the celebrity means that the main focus of the

Rays when 2 or a lot of Reflexions or Refrac-

tions could also be found.

Caf: 4. Let ACBD [in Fig. 7.] be any refrac-

ting Lens, ſpherically umbellate or cup-shaped or

Plane on either ſide, and let CD be its Axis

(that is that the Line that cuts each its Surfaces

perpendicularly, and paſſes through the Centers

of the Spheres,) and during this Axis created let

F and f be the Foci of the refracted Rays found as

above, once the incident Rays on each each the Lens area unit Parallel to the celebrity Axis; and upon the Diameter F f bifected in E, deſcribe a Circle.

Suppoſe currently that any purpose letter be the main focus of

any incident Rays. Draw QE cutting the ſaid

Circle in Tandt, and in that take t g in ſuch

Proportion to East E or TE hath to TQ.

Let metal caustic the contrary method from t that TO

doth from T, and letter letter be the main focus of the

refracted Rays with none with none, pro-

vided the purpose letter be not ſo remote from the

Axis, nor the Lens field-grade officer broad on create any of

the Rays fall too obliquely on the refracting

Surfaces.

And by kind Operations could the reflective

or refracting Surfaces be found once the 2

Foci area unit given, and thereby a Lens be fashioned,

which that create the Rays flow towards or from what place you pleaſe.

So then the which means of this Axiom is, that

if Rays discover any Plane or Spherical Surface or Lens, and before their Incidence be due

or towards any purpose letter, they ſhall when Re-

flexion or Refraction be due or towards the

Point

Soon

[ II ]

purpose nine found by the preceding Rules. And if

the incident Rays result or towards ſeveral

points Q, the mirrored or refracted Rays fhall

flow from or towards ſo several alternative Points alphabetic character

found by the celebrity Rules. whether or not the reflect-

ed and refracted Rays result or towards the purpose alphabetic character is eaſily familiar by the ſituation of that time.

For if that time air air ſide

of the reflective or refracting Surface or Lens

with the purpose alphabetic character, and also the incident Rays flow

from the purpose O, the mirrored flow towards

the Point g and also the refracted from it, and if the incident Rays flow towards alphabetic character, the mirrored result alphabetic character, and also the refracted towards it.

and also the contrary happens once g is on the opposite fide of that Surface.

A X. VII.

where the Rays that come back from all the

Points of any Objeɛt meet once more in ſo several

Points when they need been created to converge by Reflexion or Refraction, there they're going to build an image of the thing upon any wbite Body on that they fall.

thus if PR [in Fig. 3.] repreſent any Object with-

out Doors, and A B be a Lens placed at a hole

in the Window-shut of a dark Chamber, where- by the Rays that come back from any purpose alphabetic character of that Object area unit created to converge and meet a- gain within the purpose alphabetic character; and if a Sheet of white Pa- per be command at q for the sunshine there to fall on it: the Pieture of that Object PR can ap- pear upon the Paper in its correct correct and Co-

lours

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