Atlas of Absorption Spectra (Classic Reprint) - Softcover

Uhler, Horace Scudder

Softcover

ISBN 10: 1528402723 ISBN 13: 9781528402729

Verlag: Forgotten Books, 2017

Inhaltsangabe

Excerpt from Atlas of Absorption Spectra

For the removal or transmission of one or more isolated lines some other arrangement is often more useful than an absorbing screen. A spectroscope with a slit placed in the focus of the observing telescope (monochromatic illuminator) is frequently all that is necessary. But if more light is required, the following device may be used. A block of quartz from 2 to 4 cm. In thickness, cut perpendicular to the optic axis, is mounted between two Nicol prisms. The transmitted spectrum is crossed by black bands, which result from the rotatory power of the quartz. By adjusting the nicols and varying the thickness of the quartz it is often possible to get rid of the spectrum lines which are not desired, and at the same time to utilize the whole area of the source, which can never be done with the spec trosc0pe. In this way, with a quartz plate 45 mm. Thick, the line 4809 of the zinc arc in quartz can be completely removed and the two lines 472 r and 4679 transmitted. This method is especially useful in the study of the fluorescence excited in various bodies by monochromatic light.

If it is necessary to separate radiations of very nearly the same wave length, for example if we wish to work with the light of one of the two sodium lines, the following arrangement can be used A quartz plate about 2 cm. In thickness, cut parallel to the axis, is mounted between crossed nicols, with its axis making an angle of 45° with the principal planes of the polar izing prisms. The source is placed behind a vertical slit 2 or 3 mm. In width, and the light, after traversing the polarizing system is brought to a focus by a lens. A number of concentric maxima and minima will be formed, the light of D1 and D, being found in adjacent maxima. The wave-length which is not desired can be stopped by a screen of suitable dimensions placed at the focus of the lens. In this way it is possible to obtain a source of D1 or D: radiation of sufficient intensity to show distinct fringes in a Michelson interferometer. By a curious coincidence this method occurred independently to the writer and to Professor Michelson on the same day. It has been found to give excellent satisfaction. The thickness of the quartz plates used in either of the above cases depends upon the close ness of the lines which it is desired to separate.

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Details zur Ausgabe

• Verlag: Forgotten Books
• Erscheinungsdatum: 2017
• Sprache: Englisch
• ISBN 10: 1528402723
• ISBN 13: 9781528402729
• Einband: Taschenbuch
• Anzahl der Seiten: 118
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