The intensity of the secondary light is no longer to be arrived at by addition of individual intensities, but must be calculated with consideration of the particular phases involved.
Taylor Jones subsequently found a good agreement between the theoretical and the observed values of the tractive force in fields ranging up to very high intensities (Phil.
Specimens of curves showing the relation of induction to magnetic field at various temperatures, and of permeability to temperature with fields of different intensities, are given in figs.
When the interval is very small the discrepancy, though mathematically existent, produces no practical effect, and the illumination at B due to P is as important as that due to A, the intensities of the two luminous sources being supposed equal.
The occurrence of sin 4 as a factor in (6) shows that the relative intensities of the primary light and of that diffracted in the direction B depend upon the condition of the former as regards polarization.
Bolometric methods may be used with facility and advantage in the investigation of the distribution of intensities in continuous or semi-continuous spectra but difficulties are met with in the case of line spectra.
The present writer drew attention to this difficulty as far back as 1881, 1 when he pointed out that the different intensities of different spectral lines need not involve the consequence that in an enclosure of uniform temperature the energy is unequally partitioned between the corresponding degrees of freedom.
The unequal intensities observed indicate a difference in the effectiveness of the channels through which energy is lost, and this need not be connected with the ultimate state of equilibrium when the body is kept at a uniform temperature.
Branches must according to the above law correspond to the most refrangible of the doublets of the trunk, and if the components of the doublets have different intensities the stronger components must lie on different sides in the trunk and branch series.
The main effects we have to discuss are (I) a symmetrical widening, (2) a shift of wave-length, which when it accompanies expansion in both directions may appear as an unsymmetrical widening, (3) a change in the relative intensities of the lines.
Lithium, the relative intensities of the lines are different according as the solution is concentrated or dilute.
(f) The relative intensity of lines in the spark taken from metallic poles may be altered by the insertion of greater or smaller capacities, similarly the relative intensities are different in arc and spark spectra.
When we compare together electric discharges the intensity of which is altered by varying, the capacity, we are unable to form an opinion as to whether the effects observed are due to changes in the density of the luminous material or changes of temperature, but the experiments of Sir William and Lady Huggins 1 with the spectrum of calcium are significant in suggesting that it is really the density which is also the determining factor in cases where different concentrations and different spark discharges produce a change in the relative intensities of different lines.
A second rotation will, of course, produce a proportional augmentation of these increased quantities; and a continuance of turning will soon bring the intensities to their maximum, which is limited by an explosion between the plates" (Phil.
The enclosed area for each temperature represents the total emission of energy for that temperature, the abscissae are the wavelengths, and the ordinates the corresponding intensities of emission for that wave-length.
The ultra-violet and the visual portion are recorded photographically; Rowland's classical work shows some 5700 lines in the former, and 14,200 in the latter, on a graduated scale of intensities from moo to o, or 0000, for the faintest lines; between a quarter and a third of these lines have been identified, fully 2000 belonging to iron, and several hundred to water vapour and other atmospheric absorption.
Generally speaking, the same absorption lines are present, but with altered intensities, which differ from one spot to another.
Extreme cases of local discharge are due to the phenomena known in America as " cloud-bursts," which occasionally occur in Great Britain and result in discharges, the intensities of which have rarely been recorded by rain-gauges.
In intermediate cases the intensities of the two beams are proportional to the squares of the cosines of the angles that the principal plane of the second rhomb makes with the positions in which they have the greatest intensity.
The intensities of the incident, reflected and refracted streams are then measured in the same way, and we have merely to express that the square of the amplitude of the incident vibrations is equal to the sum of the squares of the amplitudes of the reflected and refracted vibrations.
Franz Neumann and James MacCullagh, starting from the opposite assumption of constant density and different elasticities, arrived at the same formulae for the intensities of the reflected light polarized in the principal azimuths, but in this case the vibrations must be regarded as parallel to the plane of polarization.
Half-shade analysers depend upon the facility with which the eye can distinguish slight differences in the intensities of two streams seen in juxtaposition, when the illumination is not too bright.
The field is divided into two parts that for most positions of the analyser have different intensities, and the setting is effected by turning the analyser until both halves are equally dark.
These instruments are very sensitive, but care must be taken to avoid errors caused by changes in the relative intensities of parts of the source of light - a precaution that is sometimes overlooked in furnishing polarimeters with these analysers.