Enclosing the photosphere is a truly gaseous envelope which is called the chromosphere, and which shows a spectrum of bright lines when we can isolate its emission from that of the photosphere.
The " black body " is an ideal body with surface so constituted as to reflect no part of any radiations that fall upon it; in the case of such a body Kirchhoff and Balfour Stewart showed that unless energy were to be lost the rate of emission and absorption must be in fixed ratio for each specific wave-length.
But there is always leakage of energy either through friction or through wave-emission, so that the vibration only increases up to the point at which the leakage of energy balances the energy put in by the applied force.
The latter is considered below; " The Black .,, it is i nd i cat i ve of the chemical elements from which the lines can proceed, and its state at the time of emission; the former is indicative only of the rate of loss of energy from the sun by radiation, and is inwoven with a remarkable group of physical theory and experiment, known as the theory of the black body, or as black radiation.
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.
Dyson has measured some eight hundred lines in the lower chromosphere and identified them with emission spectra of the following elements: hydrogen, helium, carbon with the cyanogen band, sodium, magnesium, aluminium, silicon, calcium, scandium, titanium, vanadium, chromium, manganese, iron, zinc, strontium, yttrium, zirconium, barium, lanthanum, cerium, neodymium, ytterbium, lead, europium, besides a few doubtful identifications; it is a curious fact that the agreement is with the spark spectra of these elements, where the photosphere shows exclusively or more definitely the arc lines, which are generally attributed to a lower temperature.
The helium formations do not reach the sun's limb, and it is another puzzling detail that the spectrum of the disk shows no absorption line of anything like an intensity to correspond with the emission line of helium in the chromosphere.
Apart then from absorption there will be a discontinuous change in brightness in the apparent disk at that value of the angular radius d which corresponds to tangential emission from the upper lever r' of this mirage-forming region.
A few of the lines show a double reversal, the dark absorption line being greatly increased in breadth and showing a bright emission line in its centre.
But the royal bank, as a state establishment, asked for compulsory privilege to increase the emission of its credit notes, and that they should receive a premium upon all metallic specie.
T Malus gave the name of polarization, as he attributed it, on the emission theory of light, to a kind of polarity of the light-corpuscles.
The integrated emission of energy is given by the area of the outer smoothed curve (4), and the conclusion from this one holograph is that the " solar constant " is 2.54 calories.
In addition to the above facts of polarization mention may be made of the partial polarization, in a plane perpendicular to that of emission, of the light emitted in an oblique direction from a white-hot solid, and of the polarization produced by diffraction.
This production is not a physical process, but an emission of force; and, since the product has real existence only in virtue of the original existence working in it, Neoplatonism may be described as a species of dynamic pantheism.
The emission of rays like those just mentioned - as a property of some undiscovered substance, submitted pitchblende to a most careful analysis.
On the tree being lifted from its hole the roots should be examined, and all which have been severed roughly with the spade should have the ends cut smooth with the knife to facilitate the emission of fibres.
In 1877 a financial crisis occurred, met by the emission of paper money, but the depression was only temporary, and the country soon rallied from the effects.
Finally, a fifth type has been added, the Wolf-Rayet stars; these show a spectrum crossed by the usual dark lines and bands, but showing also bright emission bands of blue and yellow light.
On the 25th of April 1900 a law was enacted for the regulation of the constitution, capital, note emission and metallic reserves of banks.
Evershed 3 has shown that in this and other cases the temperature at which emission becomes appreciable is about 700°.
Spectra has been recognized, in which, as well as the usual absorption bands, bright emission lines of hydrogen appear; stars having this particular spectrum are always variable.