scholarly journals Measurement of rotatory dispersive power in the visible and ultra-violet regions of the spectrum

1908 ◽  
Vol 81 (550) ◽  
pp. 472-474 ◽  
Keyword(s):  
Photographic Plate ◽  
Monochromatic Light ◽  
Green Light ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Narrow Strip ◽  
In Series ◽  
Limited Scale ◽  
Dispersive Power ◽  
Constant Deviation

The following is a brief preliminary account of improvements effected in the method of determining rotatory dispersive power which have made it possible to observe accurately not only in the bright regions of the visible spectrum, but throughout the scale from the region of the lithium red line into that commanded by the photographic plate. Two methods have generally been used for the purpose, namely, (1) Broch’s method, in which a spectroscope is arranged in series with the polarimeter and a narrow strip of a continuous spectrum is picked out for observation—a method which is much improved by using a constant-deviation spectroscope in place of one of the variable-deviation type, and .(2) Landolt’s method, in which a white light is reduced by means of filters to approximate homogeneity in the red, green, light-blue, or dark-blue parts of the spectrum. Neither method fulfils the fundamental condition that the field of the polarimeter shall be uniformly lighted with monochromatic light—many of the measurements that have been made, therefore, possess only a qualitative value. A much better method is due to the late Sir William Perkin, who introduced the use of a spectroscope-eyepiece as a means of purifying the sodium light, and used it on a limited scale for measuring rotatory dispersive power in the red (lithium), yellow (sodium), and green, thallium) parts of the spectrum.

THE SPECIFIC EFFECTS OF MONOCHROMATIC LIGHT ON THE GROWTH OF YEAST

1930 ◽  
Vol 2 (4) ◽  
pp. 249-263 ◽  
Author(s):  
A. H. Hutchinson ◽  
Dorothy Newton
Keyword(s):  
Growth Rate ◽  
Rapid Growth ◽  
Monochromatic Light ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Light Stimulation ◽  
Specific Effects ◽  
Rapid Growth Rate ◽  
Sudden Transition

An isolated strain of Yeast, derived from Fleischman's preparation, when exposed to monochromatic light responds quite differently to light of different wave-lengths. Slight retardation in growth by red and orange light, stimulation by yellow and green, and increasingly marked retardation in the blue and violet, characterize the effects of the mercury lines of the visible spectrum. There is a sudden transition to stimulation in the near ultra-violet. (λ 3984 Å). Stimulation continues at λ 3650 Å and characterises the region λ 2894 Å to λ 2700 Å, but otherwise the lines employed in this investigation retard growth.Generally the effect either of stimulation or retardation is greater when the control is one of rapid growth rate, but the reverse is the case at the red end of the visible spectrum.

scholarly journals Further spectra associated with carbon

1925 ◽  
Vol 108 (746) ◽  
pp. 343-355 ◽  
Keyword(s):  
Visible Spectrum ◽  
Ultra Violet ◽  
Line Spectrum ◽  
Band Spectrum ◽  
Comet Tail ◽  
Experimental Conditions ◽  
Negative Band ◽  
In Series ◽  
Condensed Discharge ◽  
Band Spectra

In a recent paper by Professor Merton and myself, an investigation was made of the experimental conditions effecting the isolation of some familiar band-spectra of Carbon. In particular, we made a study of the action of Helium in isolating and modifying spectra associated with this element. It was found that under appropriate conditions some new spectra of Carbon were isolated. With a trace of an oxide of Carbon in some 20 to 30 mm. of Helium an uncondensed discharge produced a band system identical with that found by Pluvinet and Baldet in the spectrum of comet tails, and which was afterwards discovered by Fowler to be characteristic of CO at extreme low pressures. Tubes prepared in this way and subjected to a mild condensed discharge yielded a spectrum consisting only of the lines and bands of Helium, and a number of new lines which were attributed to Carbon. A notable feature of the latter spectrum was the bright line at λ 5380, recorded previously only as a Carbon line of small intensity. The characteristic spark lines λλ 6583, 6578, 4267, were also absent, or of very doubtful occurrence, and the conditions of excitation led us to suggest that this line spectrum might be the true “arc” spectrum of Carbon, which the energy of the ordinary arc was insufficient to produce, and that of the condensed spark sufficient to repress. Both the line-spectrum and the Comet-Tail bands were investigated only in the visible spectrum; in the present paper observations and measurements of these spectra in the ultra-violet are recorded. In addition, a new band-spectrum apparently associated with the Comet-Tail bands has been measured and expressed by a series formula. The opportunity afforded by the exceptionally strong development of the first negative band-spectrum of Carbon has been taken to re-measure these bands and dispose them in series. Finally, the significance of some of these phenomena is discussed.

scholarly journals An improved method of ultra-violet anomalous rotary dispersion of sodium tartrate

1928 ◽  
Vol 119 (783) ◽  
pp. 706-709
Keyword(s):  
Wave Length ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Rotatory Power ◽  
Rotatory Dispersion ◽  
Improved Method ◽  
Sodium Tartrate ◽  
Approximate Form ◽  
Rotary Dispersion ◽  
In Series

A large number of ultra-violet polarimetric measurements have been made by a method described by one of us in 1908.* In this method a triple-field polarimeter, with Foucault in place of Nicol prisms, is arranged in series with a quartz or quartz-calcite spectrograph. A quartz-calcite lens, replacing the eyepiece of the polarimeter, casts a real image of the triple field on the slit of the spectrograph, and thus gives rise to a triply divided spectrum, intersected by dark bands. The wave-length corresponding with a given rotation is determined by finding a line which is of equal intensity in the three fields. The approximate form of the curve of rotatory dispersion can be determined by setting the analyser in a series of positions separated by 5° or 10° ; but it is then advisable to “bracket” some of the more conspicuous lines by making fresh exposures at intervals of perhaps 0·2°, when the rotation corresponding with the wave-length of a given line can be determined within about 0·1°. This degree of accuracy is less than that which can be reached in the central part of the visible spectrum, where the readings may be reproduced under favourable conditions within about 0·01° ; but it is not appreciably less than the accuracy of visual readings in the red and violet regions, and for many purposes is quite satisfactory. Thus, with a column of quartz 496 mm. in length, readings to 1° sufficed to give the rotatory power in degrees per milli­metre within 0·002°, corresponding with an error of about 1 part in 100,000 at wave-length 2327. The present investigation was undertaken in order to find out whether the same apparatus could be used to record with sufficient accuracy the much smaller rotations of solutions which had been largely diluted, in order to render them transparent in a region near to (or covered by) an absorption band. For this purpose the concentration is often reduced to I per cent. : the observed rotations may then be of the order of 0·5°, and must be read to 0·01° or less in order to give a true impression of the form of the curve of rotatory dispersion.

Optical properties of laser sintered polyamide 12

2015 ◽  
Vol 21 (4) ◽  
pp. 443-448 ◽  
Author(s):  
Mengqi Yuan ◽  
David L. Bourell
Keyword(s):  
Optical Properties ◽  
Plate Thickness ◽  
Monochromatic Light ◽  
Green Light ◽  
Wavelength Dependence ◽  
Light Transmittance ◽  
Content Type ◽  
Light Emitting ◽  
Polyamide 12 ◽  
Lighting Conditions

Purpose – The purpose of this paper is to report selected optical properties of laser sintered polyamide 12 blank plates under different monochromatic and white light conditions and to apply these properties in production of laser sintered lithophanes. Design/methodology/approach – A UNICO 1201E spectrophotometer was used to measure the transmittance of laser sintered polyamide 12 plates as a function of plate thickness. Monochromatic light-emitting diodes were used to assess the wavelength dependence on the transmission and contrast as captured by a SONY DSC-W55 camera. Findings – The transmittance decreased with increasing plate thickness which varied significantly depending on the monochromatic wavelength. Highest transmission was observed using green light (525 nm) and poorest transmission was measured for yellow light (589 nm). Research limitations/implications – There is a limit to the amount of contrast obtained in polyamide lithophanes because the thickness of the plates is limited to less than about 5 mm. Greater thickness results in discernible topology on the lithophane which impairs the quality of the image. Originality/value – Light transmittance of polyamide 12 plates under different lighting conditions is reported and applied to optically defined laser sintered lithophanes.

Characterization of Quantum well Structures Using Microscope-Spectrophotometry

1993 ◽  
Vol 324 ◽  
Author(s):  
Rachel M Geatches ◽  
Karen J Reeson ◽  
Alan J Criddle ◽  
Roger P Webb
Keyword(s):  
Quantum Wells ◽  
Spectral Reflectance ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Measurement Range ◽  
Aluminium Content ◽  
Quantum Well Structures ◽  
Nondestructive Characterization ◽  
Reflectance Measurements

AbstractIn this paper the application of microscope-spectrophotometry to the nondestructive characterization of a variety of multi-layer GaAs/A1GaAs structures, is described. Spectral reflectance results are used to indirectly determine variations in aluminium content, and the interdependency of aluminium content with layer thicknesses. The penetration depth of light from the visible spectrum is assessed from the correlation between spectral reflectance measurements and fitted optical models. Finally, a series of single quantum wells are investigated, and it is concluded that a significant improvement in the characterization of these materials will be achieved with an extension of the spectral measurement range into the ultra violet.

scholarly journals THE SENSIBILITY OF THE NOCTURNAL LONG-EARED OWL IN THE SPECTRUM

1940 ◽  
Vol 23 (6) ◽  
pp. 709-717 ◽  
Author(s):  
Selig Hecht ◽  
Maurice Henri Pirenne
Keyword(s):  
Infrared Radiation ◽  
Energy Content ◽  
Green Light ◽  
Visible Spectrum ◽  
Low Light ◽  
Light Intensities ◽  
Different Parts

Infrared radiation (750–1500 mµ) produces no iris contraction in the typically nocturnal long-eared owl even when the energy content is millions of times greater than that of green light which easily elicits a pupil change. The energies in different parts of the visible spectrum required for a minimal iris response yield a spectral visibility curve for the owl which is the same as the human visibility curve at low light intensities. Functionally, the owl's vision thus corresponds to the predominantly rod structure of its retina, and the idea that nocturnal owls have a special type of vision sensitive to infrared radiation for seeing in the woods at night is erroneous.

IV.—The Absorption of Light by Inorganic Salts. No. VIII. Alcoholic Solutions of Copper, Cobalt, and Nickel Salts in the Ultra-Violet

1914 ◽  
Vol 33 ◽  
pp. 44-48
Author(s):  
Alex. R. Brown
Keyword(s):  
Visible Spectrum ◽  
Ultra Violet ◽  
Inorganic Salts ◽  
Quantitative Measurements ◽  
Absorption Of Light ◽  
Cobalt And Nickel

The salts experimented on in this research were the chlorides, bromides, nitrates, and sulphates of copper, cobalt, and nickel. They were obtained from Kahlbaum. Jones and his co-workers have already investigated qualitatively the absorption of alcoholic solutions of some of these salts. Also quantitative measurements of the absorption at a few points in the visible spectrum have been made by Vaillant for some of the hydrated salts. In the present case solutions of the anhydrous salts were examined.

Effects of different monochromatic LED light colours on fear reactions and physiological responses in Mulard ducks

2017 ◽  
Vol 57 (6) ◽  
pp. 1128 ◽  
Author(s):  
Radi A. Mohamed ◽  
Usama A. Abou-Ismail ◽  
Mustafa Shukry
Keyword(s):  
Tonic Immobility ◽  
Leukocyte Count ◽  
Physiological Responses ◽  
Red Light ◽  
Monochromatic Light ◽  
Plasma Concentrations ◽  
Green Light ◽  
Total Leukocyte Count ◽  
Physiological Indicators ◽  
And Performance

Although the effects of monochromatic light on behaviour and performance of birds have been extensively studied, it is not known how rearing Mulard ducks in different monochromatic lights affects their fear reactions, physiological responses to stress and welfare. A total of 108 newly hatched Mulard ducks, representing three replicates, were housed in either blue light (BL), green light (GL), red light (RL) or white light (WL) for 12 weeks. Ducks were exposed to a light/dark schedule of 23 L/1 D, and food and water were provided ad libitum. At the beginning of the 13th week of the rearing period, behavioural measurements of fear were assessed by using a tonic immobility test, open field test and fear of man test. Physiological responses of the birds to stress such as heterophil : lymphocyte ratio, total leukocyte count and plasma concentrations of corticosterone were also assessed. Results demonstrated that birds exposed to both RL and WL displayed higher levels of behavioural indicators of fear including tonic immobility durations (P < 0.01), latency to first immobilisation (P < 0.001) and avoidance of man index (P < 0.001), and higher levels of physiological indicators of stress such as heterophil : lymphocyte ratios (P < 0.001) and plasmas concentrations of corticosterone (P < 0.001), and lower total leukocytic counts (P < 0.01) compared with birds exposed to either BL or GL. Rearing Mulard ducks in BL or GL appeared to reduce their fear reactions and physiological responses to stress and to enhance their ability to cope with the environment and may therefore improve their welfare.

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