Coarse Gratings Research Articles

The use of coarse gratings to find the refractive index of liquids

The use of coarse gratings to find the refractive index of liquids

On the optical properties of a biprism combined with a coarse grating

On the optical properties of a biprism combined with a coarse grating

Use of coarse gratings to find the refractive index of materials

Use of coarse gratings to find the refractive index of materials

Luminance thresholds for the resolution of visual detail during dark adaptation.

Luminance thresholds for the visual resolution of various widths of alternating light and dark lines were determined at various times during dark adaptation. The finest gratings, representing high degrees of visual acuity, show only a single cone curve that drops from a high luminance threshold during the first moments of dark adaptation to a final steady level that is reached after about 7 to 10 minutes in the dark. Coarse gratings produce a duplex curve that shows an initial cone portion and a delayed rod portion. Visual acuity is a parameter that sets the position of a given curve on the log threshold axis. The higher the degree of resolution required, the higher the dark adaptation threshold. At a constant grating luminance, visual acuity rises rapidly to a maximum during dark adaptation; the higher the luminance, the earlier and more rapid the rise and the higher the maximum. Visual acuity increases at all dark adaptation times with increase in luminance.

Further Observations of Magnitude with a Coarse Grating

Further Observations of Magnitude with a Coarse Grating

Monochromatic Magnitudes Observed with a Coarse Grating

Very low dispersion spectra obtained with a coarse grating in front of a 30-inch reflector were used to determine magnitudes at 5980 A. and 4480 A. From internal evidence, and from comparisons (rather few in number) with Hogg and Mason's photoelectric work, the standard error of the mean magnitudes derived is about |$\pm{0}^\text{m}.05$|⁠. Comparison with Dr Gascoigne's work indicates that the standard error of the gradients is ±0.08. The method is capable of extension to the tenth magnitude without unduly long exposure time.

Optical theory of the echelette grating

The optical properties of reflecting echelette gratings, used in the infra-red region of the spectrum, are discussed theoretically. Expressions are derived for various important characteristics including the wave-length relationship, the dispersion and the resolving power of spectrometers using such gratings. The intensity distribution is discussed and illustrated by reference to a particular spectrometer fitted with a grating of 1200 lines to the inch. The relative importance of other factors such as the variation of available energy with wave-length, the dispersion of the preliminary optical system, etc., is considered and tabulated. Particular consideration is given to the properties of such gratings when used in much higher orders of interference than are common at present. With large aperture spectrometers, this possibility of using comparatively coarse gratings with a high order of interference is of great practical importance.

Spectrophotometric Observations of the Minimum of ζ Aurigae.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrophotometric Observations of the Minimum of ζ Aurigae. Wirtanen, C. A. Abstract The variation in brightness of ~ Aurigae during the recent eclipse has been observed photographically at eight different wave lengths, using the io-inch Cooke camera equipped with a coarse grating and a low-dispersion prism. Plates were measured with the Schilt microphotometer. Seven early-type stars in the same field, ranging from 3.3 to 7.3 mag., served to establish the zero point and the scale at each wave length Publication: The Astrophysical Journal Pub Date: July 1940 DOI: 10.1086/144206 Bibcode: 1940ApJ....92..122W full text sources ADS |

On spectrophotometry in the visible and ultra-violet spectrum

In a previous communication the use of the neutral wedge for the determination both of the photographic and absolute intensities of spectrum lines has been discussed, and the results of its application to the study of certain phenomena relating to the spectra of hydrogen and helium have been given. The method has been found to be simple and convenient for the study of the relative intensities and of the structure of broadened lines in the visible spectrum. There are, however, certain features of the method which under some circumstances limit its application; in particular the density of the “neutral” wedge increases with the wave-number, and for the investigation of the ultra-violet down to λ = 2000 A, the method is at present inapplicable. Although it might be possible to construct wedges of crown glass with a very small angle for use in the ultra-violet, the fact that a number of such wedges would be required for different ranges would destroy the principal advantage of the method. Whilst no special precautions are required in the investigation of extended sources of light, it is evident that when small sources of light are used it is of the utmost importance to ensure that that portion of the slit which is behind the wedge is uniformly illuminated before the wedge is put into position, and in the case of selected regions of a source of light, e. g. , the spectrum from a particular point in the electric arc, it is only possible to obtain correct results by means of devices which entail a very considerable loss of light. The present communication relates to a method which, whilst not superior to the wedge method in accuracy, has the advantage that it can be used in any part of the spectrum which can be photographed through quartz lenses and prisms, and its application to the extreme ultra-violet beyond λ = 2000 A should present no serious difficulty. The method consists in crossing the dispersing system, e. g. , the prism of the spectrograph, with a very coarse grating, and reducing the length of the slit to a very small value. The grating is inserted between the prism and the camera lens of the spectrograph with the rulings perpendicular to the refracting edge of the prism, and a continuous spectrum thus appears on a plate as a dark central strip with a succession of other strips of different intensities on either side, the intensities of these orders being determined by the ruling of the grating and the width of the strips by the length of the slit. In the case of a discontinuous spectrum the "lines” are found to consist of dots of different intensities on either side of the central dot. It is evident that if the last dots which are just visible in the case of two lines are noted, a previous knowledge of the relative intensities of the different orders corresponding to these dots at once enables the relative intensities of the lines to be determined. It will be noted that the fact that the slit is reduced to a point not only enables different regions of a light source to be investigated without difficulty, but suggests a further application, which will be considered later, in the study of stellar spectra.

The Interferences Observed on Viewing One Coarse Grating Through Another, and on the Projection of One Piece of Wire Gauze by a Parallel Piece

The Interferences Observed on Viewing One Coarse Grating Through Another, and on the Projection of One Piece of Wire Gauze by a Parallel Piece