An Elementary Treatise on Geometrical Optics

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1888 Excerpt: ... without colour. This Newton conceived to be impossible, without at the same time making the deviations of the two prisms counteract one another, so that the whole deviation of the pencil would disappear. This made him despair of improving refracting telescopes, and led him to turn his attention to the application of ... Read More

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1888 Excerpt: ... without colour. This Newton conceived to be impossible, without at the same time making the deviations of the two prisms counteract one another, so that the whole deviation of the pencil would disappear. This made him despair of improving refracting telescopes, and led him to turn his attention to the application of mirrors to these instruments. Newton's mistake was first discovered by a gentleman named Chester Moor Hall, who made the first achromatic telescope. This discovery, however, was allowed to fall into oblivion, until the experiment was again tried by Dollond, an optician in London, who found that the dispersion could be corrected without destroying the deviation, and therefore that Newton's conclusion was not correct. We have seen, however, that different coloured rays are not dispersed in the same proportion by different substances; or in other words, that the spectra formed by prisms of different substances are not geometrically similar. Hence, if the prisms be arranged so as to unite two rays (for example, the extreme red and the extreme violet rays) in the emergent beam, there will be still a small dispersion of the other rays. Thus the beam instead of emerging quite colourless, will form a second but much smaller spectrum; this is called the secondary spectrum. Also, it will be found that by using three prisms of three different materials, three rays of the emergent beam (for example, the red, green and violet) may be united; but still, owing to the irrationality of dispersion, the other rays will not be quite united, and there will be another still smaller spectrum called a tertiary spectrum; and so on indefinitely. In theory, therefore, it is impossible to attain perfect achromatism, without the use of a very large number of different medi... Read Less

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  	Edition: 1888, University Press Hardcover, Good	Details: Publisher: University Press Published: 1888 Language: English Alibris ID: 16136795439	Shipping Options: Standard Shipping: $4.69 Choose your shipping method in Checkout. Costs may vary based on destination.
  Seller's Description: Good. Ex-library copy with usual markings. Cover shows minor wear and tear, rubbing and edgewear, loss on the spine. Pages are lightly tanned and clean. Very Clean Copy-Over 500, 000 Internet Orders Filled.
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