Optical Instruments Volume 2

Optical Instruments Volume 2

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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. 1871 edition. Excerpt: ...and VI.) the images of objects formed by a convex lens or combination of lenses, have been confined within a tube, and viewed by an eyepiece; but by the omission of the eye-piece, and the employment of a screen to receive the image, a picture is formed which can be viewed at once by a whole assembly of spectators. THE MAGIC LANTEHN. The magic lantern is an instrument for exhibiting on a screen an enlarged view of pictures painted on glass with transparent colours. It has already been explained (p. 22), that when an object is placed at a distance from a lens greater than its focal length, a real image of this object is formed on the other side of the lens. When the object is at a distance from the lens equal to twice its focal length, the magnitude of the image is equal to that of the object; and as the object is moved nearer and nearer towards the principal focus, the magnitude of the image is increased more and more, to an unlimited extent. The extent to which the magnifying power may be made available is, however, limited by the amount of light which can be thrown on the object, and by the indistinctness arising from the spherical and chromatic aberration, which increases with the magnification of the image. In its simplest and cheapest form the magic lantern consists of a dark lantern, with a bent chimney, to carry off the smoke and heated air with no emission of light. Within the lantern a lamp L, with an Argand burner, is placed, to give a powerful light; behind the lamp is a reflector, B, to increase the illumination; and in front of it, and on a level with its flame, is a tube, in which is fixed a large plano-convex lens, c, to condense the light irpoi'. the picture, which slides through a groove, Bb, formed-updn the tube. The tube is...
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Product details

  • Paperback | 72 pages
  • 189 x 246 x 4mm | 145g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 123655437X
  • 9781236554376