The Elements of Optics: Designed for the Use of Students in the University

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J. Burges, sold by J. Deighton, 1801 - 251 pages
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Page 195 - ... oblong and not oval, but terminated with two rectilinear and parallel sides, and two semicircular ends. On its sides it was bounded pretty distinctly, but on its ends very confusedly and indistinctly, the light there decaying and vanishing by degrees. The breadth of this image answered to the sun's diameter, and was about two inches and the eighth part of an inch, including the penumbra. For the image was eighteen feet and...
Page 194 - Chamber, at a round Hole, \- about one third Part of an Inch broad, made in the Shut of a Window, I placed a Glass Prism, whereby the Beam of the Sun's Light, which came in at that Hole, might be refracted upwards toward the opposite Wall of the Chamber, and there form a colour'd Image of the Sun.
Page 196 - Success of the Experiment according to the quantity of the Refraction. It is farther to be observed, that the Rays went on in right Lines from the Prism to the Image, and therefore at their very going out of the Prism had all that Inclination to one another from which the length of the Image proceeded, that is, the Inclination of more than two degrees and an half. And yet according to the Laws of Opticks vulgarly received, they could not possibly be so much inclined to one another.* For let EG [Fig.
Page 195 - I stopped the prism, and fixed it in that posture, that it should be moved no more. For in that posture the refractions of the light at the two sides of the refracting angle, that is, at the entrance of the rays into the prism, and at their going out of it, were equal to one another.
Page 195 - I let the refracted light fall perpendicularly upon a sheet of white paper at the opposite wall of the chamber, and observed the figure and dimensions of the solar image formed on the paper by that light. This image was oblong and not oval, but terminated with two rectilinear and parallel sides, and two semicircular ends.
Page 197 - Image, and is refracted in the Prifm at K and H, and the latter comes from the higher part of the Sun to the lower part of the Image, and is refracted at L and J.
Page 196 - It is farther to be obferved that the rays went on in flraight lines from from the prifm to the image, and therefore at their going out of the prifm had all that inclination to one another from which the length of the Image proceeded. This image...
Page 195 - ... through the middle of the prifm, from one end of it to the other end, parallel to the edge of the refracting angle) was in this and the following experiments perpendicular to the incident rays. About this axis I turned the prifm flowly, and faw the refrafted light on the wall, or coloured image of the fun, firft to defcend, and then to afcend.
Page 195 - ... inch, including the penumbra. For the image was eighteen feet and a half distant from the prism; and at this distance that breadth, if diminished by the diameter of the hole in the window-shut, that is by a quarter of an inch, subtended an angle at the prism of about half a degree, which is the sun's apparent diameter. But the length of the image was about ten inches and a quarter, and the length of the rectilinear sides about eight inches, and the refracting angle of the prism whereby so great...
Page 6 - ACN, which the line defcribed by the incident ray contains, with the perpendicular to the refracting furface at the point of incidence, is called the angle of incidence...

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