Opticks: or, a treatise of the reflexions, refractions, inflexions and colours of light. Also two treatises of the species and magnitude of curvilinear figures / By Sir Isaac Newton, Knt.

Isaac Newton

Date:: 1721

Credit: Opticks: or, a treatise of the reflexions, refractions, inflexions and colours of light. Also two treatises of the species and magnitude of curvilinear figures / By Sir Isaac Newton, Knt. Source: Wellcome Collection.

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$aa] Point g found by the foregoing Rules. And if the incident Rays flow from or towards feveral points Q, the reflected or refracted Rays hall flow from or towards fo many other Points ¢ found by the fame Rules. Whether the reflect- ed and refracted Rays flow from or towards the Point g is eafily known by the fituation of that Point. ‘For if that Point be on the fame fide of the reflecting or refracting Surface or Lens with the Point Q, and the incident Rays flow from the Point Q, the reflected flow towards the Point g and the refracted from it; and if the incident Rays flow towards Q, the refletted flow from g, and the refracted towards it. And the contrary happens when g is on the other fide of that Surface. HO ais A HY Wherever the Rays which come from all the Pomts of any Objet meet again iu fo many Points after they have been made to converge by Reflexion or Refraétion, there they will make a Préture, of the Objeé upon any white Body on which they fal. Soif PR [in F7g¢. 3.] reprefent any ObjeG with- out Doors, and AB bea Lens placed at a hole in the Window-fhut of a dark Chamber, where- by the Rays that come from any Point Q of that Object are made to converge and meet a- gain in the Point g; and if a Sheet of white Pa- per be held at g for the Light there to fall up- on it; the Picture of that Obje¢ét PR will ap- pear upon the Paper in its proper fhape and Co- . | | 3 lours, 3$