High-intensity Lamps Research Articles

Microscope for use at temperatures near -190 C

A microscope is described which has been used for visual observation of ice formation at magnifications of up to 600 diameters, using both transmitted and incident light at temperatures down to -185?C. Photographs have been taken with transmitted light at magnifications, on the film, of up to 150 diameters using a 30 W, 12 V frosted lamp. For photography with incident illumination a 250 W high-intensity mercury vapour lamp and heat filter were required.

An inexpensive high intensity lamp unit for phase-contrast time-lapse cinemicrography.

An inexpensive high intensity lamp unit for phase-contrast time-lapse cinemicrography.

Isolation of atomic resonance lines by selective modulation

The resonance lines in the spectrum of an element emitted by a d.c. operated high-intensity atomic spectral lamp are selectively modulated by passage through a pulsating cloud of atomic vapour of the same element produced by an a.c. operated hollow-cathode discharge. These modulated lines produce a signal at the output of an a.c. detection system. Other lines in the spectrum produce no output signal since these are not absorbed by passage through the atomic vapour and are therefore not modulated. Thus the resonance lines are effectively isolated. The application of this technique in atomic absorption spectroscopy permits the use of much larger spectral slit-widths than are normally required, as is demonstrated by the results obtained in the determination of nickel, iron and cobalt.

A Stable, High-Intensity Vacuum Ultraviolet Source

A stable, high-intensity resonance lamp operated by a 2450 Mc/sec microwave power source has been developed which is of sufficient intensity and stability to be useful for the kinetic study of photochemical reactions. This light source has maintained a constant output (approximately 2 × 1017 quanta/sec for krypton) for times ranging from 80 h to 120 h. The optimum pressure of krypton in the lamp is 0.28 torr.

High Intensity Lamp

A long range, high intensity lamp or spotlight comprises a head portion at one end having a window opening and a handle portion connected to the head portion and containing starter circuitry for controlling operation of the lamp. A parabolic mirror is mounted in the head portion to face the window opening, and a high intensity electric arc bulb such as a Xenon bulb is adjustably mounted within the mirror so that the electrode gap is located as close as possible to the focus of the mirror. An adjustable mounting base allows the position of the bulb to be adjusted until the optimum position is reached, at which point the bulb is secured in its position.

Light sources for optical communication

Several modulated light sources of historical nature are described which have been used in transmitting intelligence to distant points. Some of the characteristics of cesium-vapor lamps and high-intensity short-are xenon lamps are described. The phenomenon of acoustical resonance in enclosed arcs is discussed.

Automatic Recarboning of Carbon-Arc Lamps

This paper describes some of the methods used to operate high-intensity carbon-are lamps continuously for several hours. The cost of special carbons and other factors limit their use. The development of less expensive methods would be a great improvement of the carbon-arc lamp.

The action spectrum for the transformation of protochlorophyll to chlorophyll a in normal and albino corn seedlings

1. 1. A monochromator has been developed for use with a high intensity lamp by means of which leaves can be illuminated throughout the visible spectrum with light monochromatic within 5 mμ. The beam is of such intensity that the protochlorophyll-chlorophyll transformation produced by periods of illumination of from 20 sec. to 6 min. is sufficient for accurate measurement. 2. 2. Methods of analysis have been worked out whereby the percentage transformation of protochlorophyll can be determined with a precision of about 2%. 3. 3. An albino mutant of corn has become available which when grown in the dark contains approximately the normal amount of protochlorophyll, and upon illumination transforms it into chlorophyll. The action spectrum for the transformation has been measured in this albino strain and in the normal strain from which it segregates. 4. 4. The two corn strains and also bean leaves show a prominent peak in the action spectrum at 650 mμ. At this wavelength 20% of the protochlorophyll was transformed to chlorophyll in 18.4 sec. by an intensity of 79.8 ergs/cm. 2/sec. 5. 5. Another prominent peak lies at 445 mμ. In normal corn and bean leaves, this peak is considerably lower than the peak at 650 mμ, the ratio being 0.66. In contrast, the albino corn uses blue light even more effectively than it does red, the ratio of the peaks at 445 and 650 mμ being 1.89. 6. 6. Since the normal corn leaves contain abundant carotenoids and the albino does not, the lower efficiency of normal etiolated leaves in the blue can be attributed to competitive absorption of light by carotenoid pigments. 7. 7. If some chlorophyll is formed by a pre-exposure to light and the leaves are then further illuminated at 680 mμ (light which is strongly absorbed by chlorophyll but only weakly by protochlorophyll) only a little additional chlorophyll is produced. The increase in chlorophyll can be attributed to the slight absorption by protochlorophyll. 8. 8. Because of the sensitivity and precision of the methods used, the action spectrum for the conversion of protochlorophyll in the leaf is known with an accuracy approaching that of the absorption spectrum of extracted protochlorophyll. The two spectra are similar and the positions of the spectra are in agreement if allowance is made for the shift due to the influence of solvent.

The Color of Light on the Projection Screen<!--<xref ref-type="other" rid="fn1-10.5594_J09914">*</xref>-->

Spectral energy distribution measurements of the light at the center of the projection screen have been made for a number of arc lamp and carbon combinations employed in motion picture projection. ICI color-coördinates and color-temperatures have been calculated and show that the various high-intensity combinations give chromaticities and color-temperatures which agree closely among themselves. The spectral-energy distribution data of both low and high-intensity lamps and carbons show marked similarity to black-body curves.

Improved Methods of Controlling Carbon Arc Position

This paper shows, both from previous data and fundamental considerations, the close control of carbon position necessary to obtain constant light on the projection screen, particularly with reflector-type high-intensity carbon arc lamps. Review of the characteristics of this type of lamp and optical system reveals that in order to obtain constant light on the screen it is necessary to avoid variation of carbon position and changes in arc current due to line-voltage fluctuations. Methods of arc control employing photoelectric cells and bimetallic thermostats directly responsive to carbon position have been analyzed with regard to their applicability for this purpose. Some examples of these have been constructed and have demonstrated that automatic devices of simple construction are capable of maintaining constant the intensity, distribution, and color of the light on the projection screen.

Trends in high-intensity mercury lamps

Although the characteristics of the mercury arc at pressures as high as two atmospheres were investigated more than 30 years ago, lack of suitable materials delayed until recent years the commercial development of practical high-pressure high-intensity mercury-arc lamps.

Colour Television at the Dominion Theatre, London

ON February 4, a surprise item was introduced into the regular programme of the Dominion Picture Theatre, London. At 8 p.m. an experimental demonstration of Baird colour television was effected for the first time in public. The sending station was the South Tower of the Crystal Palace, the wave-length employed being 8·3 metres. The quality of the pictures was naturally much inferior to those with which the present-day viewer is familiar: only 120 scanning lines being used as compared with the 400 lines now employed by the British Broadcasting Corporation. The projected picture was twelve feet by nine feet and could be clearly seen by everyone in this large theatre. It was illuminated by a high-intensity arc lamp. The programme included the transmission of fashion plates of ladies hats ; the various coloured flowers were quite brilliant and the gaily and variegated headgear sometimes used by officers abroad came out very distinctly. A coloured cartoon of Popeye the Sailor caused much amusement. Colour television is still in the early stages of development, but the transmission was very successful and the unexpected show was well received by the spectators.

Recent Developments in Gaseous Discharge Lamps

The luminous and electrical characteristics of a number of vapor discharge lamps that have attained practical importance in recent years are described. These include the sodium vapor lamp, the high-intensity mercury vapor lamp, and the high-pressure quartz capillary lamp. The fundamental physical phenomena and the manner in which these affect the light output and efficiency are discussed briefly. The effect of variations in gas pressure and current density upon the distribution of intensity in the spectrum is dealt with, and also the accompanying changes in intrinsic brilliancy and color of light emitted. — The latter part of the paper contains a discussion of recent developments in the utilization of fluorescent materials in gaseous discharge lamps. These lamps offer interesting possibilities from the point of view of general illumination and special color effects.

Effect of Light-Source Size with 16-mm. Optical Systems

An investigation of two spherical and aspheric condensers, with an f/1.65 projection lens and a test series of high-intensity biplane filament lamps ranging from 200 to 2000 watts, has been conducted to determine the levels of illumination attainable in 16-mm. projection by varying the light-source size.

High-Intensity Mercury-Arc Lamps

The general relationship between wattage and light output of high-intensity mercury-arc lamps, some of the effects of voltage and pressure on their efficiency, and a tabulation of the actual amount of energy they produce in various portions of the spectrum are discussed in this paper. The practical aspects of these lamps is discussed particularly in the fields of industrial lighting and where very high intensities of light are needed, as in searchlights, locomotive headlights, and, under certain conditions, for projection work.

Two-Way Television<!--<xref ref-type="other" rid="fn1-10.5594_J13011">*</xref>-->

An experimental two-way television system in combination with a telephone service has been installed between two buildings in New York. With this system, two people can both see and talk to each other. It consists in principle of two complete television systems of the sort previously used for one-way transmission. Scanning is accomplished by the beam-scanning method using disks containing 72 holes. Purple light, to which the photo-electric cells used are quite sensitive, is employed for scanning, and a yellow-green light is used for illuminating the television booth. High-intensity neon lamps are used with a condenser lens disk at the receiving end to give an image brilliant enough to be seen without interference from the scanning beam. A frequency band 40,000 cycles wide is required for each of the two television circuits. Synchronization is effected by a 1275 cycle alternating current, controlling synchronous motors rotated 18 times per second. Speech is transmitted by microphones and loud speakers concealed in the television booths so that no telephone instrument interferes with the view of the face.