OCR Text |
Show Of Light in order to Seeing. Book [1]; ding Reflection or Refraction ) are madein the furface of a Medium, either Line, ( as by amoft fimple motion molt fuitable to Nature) exerting its utmoll force, to promote the quick Pulfe relating to the Rays of Light. ,_ From hence the progrefs of Hays is fo far defined, as it is included with; . in Two plane Surfaces, perpendicular to the infleé‘ting Medium. dence and Refraction, are formed, as the Rays of Light are reprehented more or lefs obliquely through the Air to the Cornea, or out of any other tran‘ipa. ‘ rent Medium to another. And this Inflefiion may happen as well in a plane Surface, as a Spherical; For infiance, let 3 Ray fall upon the outfide of a Plane Looking-Glafs at fuch apoint, through which Two right lines may be drawn ; fo that the faid lines falling upon one plane Surface , What hinders the reflection of the Rays to be made in the fame Plane? And by the fame reafon a Refleé‘tionof Rays are diffufed intoan Orbe. vi ible Objeéls, and the difeovery of Figures, Magnitudes, and the explica: tion of the caufes of their 'Pbainomena, as agreeable to Reafonand Experi- ence. Wherefore the Figure of a Prifme or Cylinder ( being Mathematical.» 1y attributed to a Ray of, Light) is Conceived to be impelled in a right The motion ofgLight is made in a right Linc. Here the Ray may be Treated of, as endued only with Two Dimenfions, refembling as it were, a rectangular Parallelogram, feared in a Plane accord- ing to right Lines, at the Surface of the infleéting Medium. Another Hypothcfis belonging to Light, may be this; That the Ray of TheRay of Incidence, and Refleétion make equal Angles at the Surface of a Looking. Glafs. = » t» , V . .V Inciderce and Rcflcflion,‘ make equal Angles. Prifme or Cylinder, according to the fhape of the Body, from whence they A rectangular Parallelogram reprefenteth a Ray obliquely, falling upon the Plane of a Looking-glafs ; and when the point of a Parallelogram encountringa Looking-glafs, as an opace and impervious Body, cannot make its progrefs in a direét courfe, it endeavoureth to recoil back again in firaight Lines, and the other term of the Parallelogram ( feared in a right p‘oflure ) is elevated above the Surface of the Looking-glafs, if it be hindred by the interpolition of a dark Body, and bath its motion carried backward in a right The begin; take their rife. progrefs 5 after the Ray hath begun its refleflion on the Surface of the Look; ning of rev 5(6th Rays innumerable Rays maybe made in infinite points of a Plane Opace Body; As alfo reflected Rays may difplay themfelves into an Orbe, whereby alltht adjacent parts are receptive of greater degrees of Light, as the Beams are doubled by Reflection, which are not mere Mathematical Lines, but Bodies afl'efied with all kinds of Dimenfions, and endued with the' Figure Ola An Experi- 893 grefs of the infleéted Rays of Light, and the places of Images, belonging to pofition of a tranfparent Medium, wherein greater or lefs Angles of inci. Rays make an Of Light in order to Seeing. Opace Body in reference to reflection, or in refraé‘tion made by greater or lefs degrees of Denfity in difl‘crent tranfparent Mediums, _which is evidem in the various Coats and Humors of the Eye, through which the Rays oi Light being trajeaed, do make different Angles, and either bend to, or re, " cede from the perpendicular; {0 that the reflection of lucide Rays (inclu. by the refil'tance of a folid Body, not receptive of Light, or by the lefs op- inflection both in a Plane and phxrital Surface. Book I II. mflll to COD- For the better illufiration of this Hypothelis, Suppofe a Ray (likea Pa- firm thir Hypothefia. rallelogram) be reprefented to have its fide applied to the Surface of tlic Glafs, while the other part of the Parallelogram is lifted up above the Plant of the Glafs, and recoileth in a direél progrefs from the laid Plane, And when Nature is not difcompofed in its ufual and proper courfe, the Rays of Light do recede as little as may be from a {traight l'tream, to which they havea at. rural inclination. If a Paralleledipe be Mathematically accounted for a right Line, a reflected Ray alfo refembling it, may be conceived to be a right Line; and by the fame rcafon, if 21 Ray be endued with the Figure of a Right Cylinder, fuch a one as fireameth from a Sphzrical lucid Body, it may be [hewn to admin Refieétion, coming flraight from the Surface of a dark Body; becaufearight , Cylinder falling upon a Plane, hath its Bafis and Axis fo placed, thattht Bafe doth touch the Plane of the Looking-glafs, and the tell: of the body 0f the Cylinder is obliquely elevated above the Plane; and a line being drawn from the Ball: of the Diameter, doth obliquely interfeé‘t a line of the Axis: whereupon it being carried through it and the Axis, a Plane is made in the Cylinders; fo that through its (ides two Planes may be conceived to be drawn parallel to the Axes touching the Cylinder: Whereupon it may be made evident, that the Duét of the whole Cylinder may be comprehended between ' Two Planes, defining the reflection of the Ray between them; and their Planes are right to the Plane of the Looking-glam {0 that the faid Planes perpendicular to this touching the Cylinder, run parallel to‘ the Axis, whereupon, the fame Planes become right to the Plane of the Looking-g1al$ Hence it may be inferred, that if the Whole Radius fu ofcd to be 3 right i Line, its Refiefiion will be made, as in a Surface, bedireldi ' to the Plane 0f i‘ the Glafs. Thefe received Hypothefes, or rather Maxims relating to Light, are VC'l eonducrve to the better is made as a ing-glafs by a kind of Rotation, and then it maketh good its retrograde Moi kind of Arch; tion in a direct courfe; fo that when the Ray falleth upon the plane of the Glafs in a point (as Mathematically taken) it immediately malteth an Arch in its firft reverberation, as defleéling from a right Line, and after fiame fmall fpace recovererh its regular and proper lVIotion. as mof't agreeable to the unfpeakahle fwiftnefs of the molt minute and fubtle Bodies of Light. The Rays of Light are carried forward with an admirable Celerity, and falling in a point upon the Surface of fome opace Body ( not receptive of the beams of Light) are forced to retreat with great quicknefs, and are re: filled in the beginning of their Reflexion, with the contrary motion ofothet' themn‘ner , beams; Wheteupon the oppofite Rays do impede each others progtefs, and $3,155?" make a kind of circular Motion , which I conceive is made after this man: "We" oylce Body: net : The Rays being impelled forward, asfalling' Upon the Surface of an opace Body, do make firl't an Angle of Incidence, and as the Beams are not received into the Pores of a dark Body, they form another Angle of Reflecti- on upon the point of the Surface, from which the Rays are beaten back, at fome difiance from the other Beams; fo that the Angle of Incidence being conjoyned in the Center to the Angle of Refleétion, doth make fome part of the Semi-circle, as the Rays moving backWard, are fomewhat h‘indred by a refillance of forward Beams, which endeavour to infinuate themfelves into the Pores of the Opace Body, before they make a retrograde courfe; fo‘ that the mofi fubtle and minute Bodies of Light, being of an active, refilefs temper, do perpetually diffufe themf'elves through tranfparent Mediums, and more perpendicularly-forward, till they are flopped by fome opace Bodies, and then they are eonltrai'ned either to reft ( which is inconfiflent with the nature of Light ) or to return by Relieéti‘on. lfthc inquifitive Reader do demand a Reafon, when only a point of the Ray hath a renitence, and all the wit of the Line afl‘eéteth a contrary mo-' underflanding of Opticks, as determining the P" tion; This reply may be given, That the Incident Rays being aficdt with are at |