A New and Compendious System of Optics ...

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James Hodges, 1740 - Optical instruments - 295 pages
 

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Page 5 - CM is the reflected ray. The angle of incidence is that which is contained between the incident ray AC and a perpendicular to the reflecting surface in the point of reflection, as the angle AC D.
Page 178 - ... object, O, and view it with the eye placed in the other focus of the lens at F; and according to the focal length of the lens, the object O will appear more or less magnified, as represented at I M.
Page 176 - Diameter of the Lens; for the Rays AD and BE, which go from the Object to the Extremities of the Lens D and E, and are united at the Focus F, muft neceflarily proceed from the Object to the Lens parallel to the Axis FC, and therefore parallel to each other; confequently the Part of the Object AB, feen by the Ray's DF, EF, will be equal to the Diameter DE of the faid Lens.
Page 177 - ... of the eye. Since then it is evident the nature of a convex lens is fuch as will render an...
Page 184 - Proportion. 2. The proportion of the Sine of Incidence to the Sine of Refraction of one and the same sort of Rays out of one Medium into another, is composed of the Proportion of the Sine of Incidence to the Sine of Refraction out of the first Medium into any third Medium, and of the Proportion of the Sine of Incidence to the Sine of Refraction out of that third Medium into the...
Page 181 - In ufing thefe Spherule Microfcopes, the Objects are to be placed in one Focus, and the Eye in the other; and...
Page 175 - ... is measured by the angle under which they are seen by the eye, and those angles are reciprocally as the distances from the eye. If eight inches be assumed as the nearest limit of a distinct vision to the naked eye, and by interposing a lens, we can see with equal distinctness at a nearer distance, the object will appear to be as much larger through the lens than to the naked eye, as its distance from the eye is less than the distance of unassisted vision. If the focal distance of a convex lens...
Page 176 - DE, (Fig. 4.) it's two Foci F and C; in the Focus C let there be an Object AB larger than the Lens ; fuppofe the Rays AD, BE, proceed from the Extremities of the Object to thofe of the Lens, it is evident from the Figure they will be convergent, and therefore...
Page 3 - The Focus of rays is that point to which all converging rays tend, asO (fig. 5) : this is called the real focus. 13. The VIRTUAL or IMAGINARY Focus is a point, as f, to which the rays AB tend, and where they would...
Page 174 - It is usual to say, that the microscope magnifies the objects which are seen through it ; but this is true only with regard to the. apparent, not the real magnitude of objects ; they indeed appear to be larger with, than without a microscope ; but in truth they are not...

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