Raymond T. Birge

Interrelationships of e , h/e and e/m

IN a report1 presented some twenty months ago on the values of e, h and e/m, attention was directed to the numerous inconsistencies shown by the experimental data. More recent developments have resolved a number of these inconsistencies, and it now seems possible to reduce all the really precise experimental data in such a way that only one fundamental discrepancy remains. Because of the great amount of experimental material here involved, it is necessary to omit all details in the present brief letter. I wish merely to remark that I am now using for c the value2 2.99776 × 1010 cm./sec., in place of the former 2.99796.

On the Nature of Unpolarized Light

All that can be affirmed regarding the nature of unpolarized light is that it shows no preferential polarization. When, for instance, unpolarized light enters a quartz crystal in a direction parallel to the axis, the light is decomposed into right- and left-circularly polarized beams of equal intensity. This was demonstrated experimentally by Fresnel. By the use of right- and left-handed quartz crystals in the two paths of an interferometer, interference effects occur whose nature can be definitely predicted on the assumption of the existence of such circularly polarized components. An experiment of this nature has been performed by Langsdorf and DuBridge, but the experiment, in itself, furnishes no information as to the nature of unpolarized light.

The Energy Levels of the Nitrogen Molecule

IN a paper before the American Physical Society (Phys. Rev., 23, 294, Feb. 1924) and in a letter to NATURE (Nov. 1, 1924, vol. 114, p. 642), I gave a set of electronic energy levels for the neutral nitrogen molecule, based on an analysis of its band spectra. These levels were designated X, A, B, C, and D, where X denotes the stable state of the molecule. The interval X to A was suggested as 65,000v (= 8.0 volts), the band system corresponding to this transition being as yet unknown. Dr. Sponer (Zeitsch. f. Phys., 34, 622, 1925), by measuring the excitation potentials of various groups of nitrogen bands, has now obtained results in exact agreement with this diagram. The X to A interval comes out as 7.9 volts.

The Electronic Charge e

PROF. A. S. EDDINGTON has recently (Proc. Roy. Soc., A, 122, 358; Jan. 1929) deduced a theoretical value of 136 for the well-known ratio hc/2πe2. The reciprocal of this ratio is usually denoted ‘the fine-structure constant a.’ Without presuming in any way to judge the theory on which this value is derived, I should like to make a few remarks as to the numerical result. The value of the velocity of light c is known with great accuracy (c = 2.99796 ± 0.00004). On the other hand, the value of the Planck constant h depends primarily upon the value of the electronic charge e, and the probable error in h is almost entirely due to the probable error in e. Every method for evaluating h involves e to a positive power varying from unity to two. The average power depends upon the adopted relative weighting of the different methods. These facts regarding the connexion of e and h I discussed some years ago (Phys. Rev., 14, 361; 1919).

The Band Spectra associated with Carbon

THERE are now so many as thirteen band groups associated with carbon and its compounds. Some of these, such as the violet CN group, have been studied exhaustively, both empirically and upon the basis of the quantum theory. I have endeavoured to arrange in progressions and to assign vibrational quantum numbers to all of these groups, where such work has not yet been done, and several interesting new relations have resulted.

Physics and physicists of the past fifty years

Dr. Wigner, Members of the American Physical Society and of other Societies associated with the American Institute of Physics, and Guests: In the case of British organizations such as the Royal Society and the British Association, it is quite customary for the president to deliver an address of a general, nontechnical character. On the other hand, in the case at least of the American Physical Society, a purely technical paper is much more common. It seems to me, however, that at a meeting where several hundred technical papers appear on the program, at least one nontechnical paper may appropriately find a place.

Requirements for Graduation

1. Successful completion of 32 courses, with a maximum of one course in designated health and exercise science activities (HES-100 to HES-199), plus at least two Interim Experience courses. In other words, 34 courses are needed for graduation, 31 of which must be in courses other than physical education fitness (FIT), physical education activities (ACT) or Interim Experience (IEX) courses. (Transfer students admitted with advanced standing are also required to complete two Interim Experience courses.)