Date of Award

6-1929

Degree Type

Bachelors Essay

Degree Name

Bachelor of Science (BS)

Department

Physics

First Advisor

John R. Koch

Second Advisor

William J. Grace

Abstract

Before entering upon a discussion of the historical development of the subject of magnetic rotation, it may be well to explain briefly the nature of the phenomenon under investigation. According to the wave theory of light, the rays from any ordinary light source vibrate in every conceivable plane. If now the light is reflected from a glass surface or passed through a Nicol prism, it undergoes a change. If an attempt is made to pass the beam through a second Nicol prism, it is found that the optical axes of the two prisms must be parallel to one another or the beam will not penetrate the second one. This fact is explained by the supposition that the light which is reflected from the glass surface or which emerges from the first prism vibrates in but a single plane, and it is then said to be plane polarized. Every student of chemistry is familiar with the fact that certain organic substances, notable the naturally occurring carbohydrates, and in fact almost all organic substances which have an asymmetric carbon atom within the molecule, have the power of rotating the plane of vibration of a polarized beam through a definite angle. For example, suppose that we have the arrangement consisting of the two Nicol prisms mentioned above, and that they are so adjusted that a polarized beam from the first passes without difficulty through the second. If a tube containing a solution of ordinary cane sugar is now placed lengthwise between the two prisms so that the polarized beam, must pass through the solution in order to reach the second prism, it will he found upon looking through this prism, that the field of vision is dark, that is, the beam which was visible before is now no longer visible. Upon rotating the second prism, a point will be reached at which the optical field will have the same appearance as when no substance was interposed between the prisms, that is, the beam is again passing freely through the second. This means that it was necessary to rotate the second prism -in order to bring its optical axis into the same relation to the plane of vibration of the polarized beam which it had at the beginning of the experiment. Hence this plane of vibration must have been rotated through an angle equal to that through which it was found necessary to rotate the prism in order that the beam might pass. Any substance which possesses this property of rotating the plane of polarized light is said to be optically active.

Comments

A Thesis Submitted To Fulfill The Requirements for the Degree of Bachelor of Science, College of Liberal Arts, Marquette University, Milwaukee, Wisconsin

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