Continuous ultraviolet spectrum
Full Text
Continuous Ultraviolet Spectrum
G. Gehlhoff: Ueber eine konstante Lichtquelle mit kontinuierlichem ultravioletten Spektrum. ZS. für techn. Phys. 10, p. 224, (1920).
Usually a continuous ultraviolet spectrum is obtained either with the aid of an arc or by means of an Angra lamp (Al electrodes in water). If the first method is unsatisfactory because of its shortcomings, the second involves a sufficiently difficult setup. Therefore the author proposes, as a permanent source of continuous ultraviolet spectrum, a half-watt incandescent lamp with a metallic filament. He investigated, in parallel, two lamps: one with a tantalum filament and the other with a tungsten spiral.
The distribution of energy in the spectrum was calculated by him according to Aschkinass’s formula for metals.
The ratio of the energy in the ultraviolet part of the spectrum from \(0.3\mu\) to \(0.4\mu\) to the energy of the visible spectrum \((0.4\mu—0.8\mu)\) is \(0.22\%\), and under an overload of \(30\%\)—\(1.23\%\) for the tantalum lamp; the corresponding values for the tungsten lamp are \(1.17\%\) and \(2.02\%\). When a photographic plate is used, these ratios become still more favorable. In the same relative terms, the energy in the spectral region \(0.3\mu—0.4\mu\) relative to the energy in the region \(0.4\mu—0.5\mu\) is expressed by the following quantities:
For the tantalum lamp, \(7.2\%\); under an overload of \(30\%\)—\(17.7\%\).
For the tungsten lamp, \(16.9\%\); under an overload of \(30\%\)—\(21.6\%\).
The author’s lamps are a sphere 10 cm in diameter, filled with nitrogen or argon. A tube is sealed to the sphere, to which a quartz plate or lens is attached with cement. For ordinary absorption measurements, a tantalum strip 25 mm long and 2–3 mm wide is sufficient, with a voltage of 6–8 volts at a load of up to 20 amperes. At the same voltage (6–8 V) and the same load (15–20 amp.), a tungsten spiral of 10 mm length is sufficient, with a wire thickness of 0.5 mm. The advantages of such a source of ultraviolet light are self-evident.
T. Molodoi.