On the Hypothesis of Light Quanta

Ramsauer. Die lichtelektrische Wirkung untertheilter Lichtquanten. Ann. d. Phys., 64, p. 750, 1921.

From the point of view of the hypothesis of light quanta, radiation exists in space (outside matter) in the form of isolated wave trains, the total energy reserve of which is determined by the well-known relation \(h\nu\). Such a conception gives a simple and easy interpretation to certain physical phenomena (for example, Millikan’s experiments on the photoelectric effect), for which another explanation proves difficult. But

On the other hand, there are many facts that do not accord with the existence of light quanta. Thus, H. A. Lorentz pointed out that the ability of light waves to interfere when there is a very large path difference (more than 2,000,000 wavelengths) leads to the conclusion that the length of the path constituting a single quantum reaches 100 meters, since only waves belonging to one and the same quantum are capable of interference. Ramsauer, in the paper under review, gives yet another experimental proof of the untenability of the hypothesis under consideration.

The polarization of light (e.g., by double refraction) consists in separating quanta with one plane of polarization from quanta polarized in a perpendicular plane. In this case one may suppose that the quanta are “sorted” without being split, according to the orientation of their plane of polarization relative to the principal plane of the crystal. However, if polarized light is divided by a doubly refracting crystal into two rays, then each of them must be formed by the division of individual quanta into two parts: \(h\nu \cos^2\alpha\) and \(h\nu \sin^2\alpha\), since the angle \(\alpha\) between the principal plane of the crystal and the plane of polarization of the incident polarized beam is the same for all quanta. Moreover, the ability of the ordinary and extraordinary rays to interfere with one another likewise speaks in favor of the splitting of individual quanta under double refraction. Thus, if light quanta exist, they must be split in double polarization; and in the photoelectric effect caused by such light composed of fractions of quanta, there should be observed a distribution of photoelectron velocities as though light of a greater wavelength were acting \((h\nu \cos^2\varphi = h\nu')\). Likewise, the number of electrons corresponding to 1 calorie of absorbed energy should be smaller than in the case of ordinary light, since in the present case the radiation consists of portions of smaller individual energy, i.e., the matter again amounts, as it were, to an increase in wavelength, and the influence of the photoelectric function of the normal effect should become manifest. Ramsauer studied the photoelectric action of such doubly polarized light (250 μμ; 436 μμ; 546 μμ and weak white light) and could not detect any deviations from the usual laws of photoelectric action. Thus, in this experiment too one may see a fact that undermines the existence of light quanta and transfers the meaning of the quantum hypothesis to the nature of the atomic resonator.

G. S. Landsberg.