抄録
Lichtenberg figures are obtained on negative color films (ASA 32 and 50) and their variations in size, form and color by lowering of pressure of the surrounding gas are studied.
On positive dendritic figures, radius of the figure increases and streamers broaden with bluish violet tint (yellowish orange on color negative films) as the pressure is reduced. These tendencies are the same for all negative circular fan-shaped figures, but the rate of increase of the radius is more remarkable on the negative figures than on the positive. Red streamers on the periphery (cyan-blue on color negative films), become more conspicuous as the pressure is further reduced, while they are only faintly observable at normal atmospheric pressure. In consideration of the multilayer structure of color film, it is inferred that the positive figures are developed only in the top layer of the emulsion and that the negative figures are of such structure that the foremost edges of their streamers reached the very bottom of the layer.
As for the relation between the rate of increase in size of the figures and the pressure, the ratio of the rates R+/R- decreases and approaches to 1 as the pressure is reduced but is larger than 2 under normal pressure. These tendencies observed on color films are different from those observed by Stekolnikof and Riaschenzef on black and white dry plates.
Under low pressures of the order of 7 cm Hg and at applied crest voltage of 11.0 kV, the color of the streamers of either sign is very weak bluish violet and no trace of red streamers at the tips of negative figures is found. Under these conditions, the above shows that the figures of either sign can be regarded as developed only in the top layer of the emulsion which is in contact with the electrode bars.
