Physical OpticsAppleton and Company, 1883 - 434 pages |
Contents
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Common terms and phrases
achromatic amplitude analyser angle of incidence aperture axes beam blue bright band centre circle coincide collimator colours consider convex lens crystal curve dark bands dark lines difference of phase diffraction direction of vibration dispersion displacement distance effect elements ellipse emergent equal ether eye-piece face focal length focus formed glass grating incident light incident wave intensity lenses Let us suppose light falls M₁ medium mirror move Nicol optic axis ordinary ray P₁ parallel particle pass pencil perpendicular placed plane of incidence plane of polarisation plane polarised light plate position principal plane prism produced quartz radius red and violet red rays reflected reflexion refracted rays refracted wave refractive index rhomb right angles rotation screen screw seen slit source of light spectrum tangent telescope thickness tion transparent travelling turn velocity violet rays wave surface wave-front wave-length
Popular passages
Page 415 - ... disturbance is propagated through it, which can be calculated from electromagnetic experiments, and also observed directly in the case of light. If it should be found that the velocity of propagation of electromagnetic disturbances is the same as the velocity of light, and this not only in air, but in other transparent media, we shall have strong reasons for believing that light is an electromagnetic phenomenon, and the combination of the optical with the electrical evidence will produce a conviction...
Page 3 - The total energy of any body or system of bodies is a quantity which can neither be increased nor diminished by any mutual action of such bodies, though it may be transformed into any one of the forms of which energy is susceptible.
Page 258 - ... have its temperature raised by light from the source of the precise quality in question. In the atmosphere around the sun, therefore, there must be present vapour of sodium, which, according to the mechanical explanation thus suggested, being particularly opaque for light of that quality, prevents such of it as is emitted from the sun from penetrating to any considerable distance through the surrounding atmosphere.
Page 259 - Fraunhofer had remarked that in the spectrum of the flame of a candle there appear two bright lines, which coincide with the two dark lines D of the solar spectrum. The same bright lines are obtained of greater intensity from a flame into which some common salt is put. I formed a solar spectrum by projection, and allowed the solar rays concerned, before they fell on the slit, to pass through a powerful salt-flame. If the sunlight were sufficiently reduced, there appeared in place of the two dark...
Page 259 - The spectrum of the Drummond light contains, as a general rule, the two bright lines of sodium, if the luminous spot of the cylinder of lime has not long been exposed to the white heat ; if the cylinder remains unmoved these lines become weaker, and finally vanish altogether. If they have vanished, or only faintly appear, an alcohol flame into which salt has been put, and which is placed between the cylinder of lime and the slit, causes two dark lines of remarkable sharpness and fineness, which in...
Page 261 - It is evident that such a medium, on being agitated, would give out the note above mentioned ; while, on the other hand, if that note were sounded in air at a distance, the incident vibrations would throw the strings into vibration, and consequently would themselves be gradually extinguished, since otherwise there would be a creation of vis viva. The optical application of this illustration is too obvious to need comment.
Page 418 - The difference between these numbers is greater than can be accounted for by errors of observation, and shows that our theories of the structure of bodies must be much improved before we can deduce their optical from their electrical properties. At the same time, I think that the agreement of the numbers is such that if no greater discrepancy were found between the numbers derived from the optical and...
Page 141 - ... feet and eleven inches radius, and quick-silvered over on the convex side. And holding a white opake chart, or a quire of paper at the centre of the spheres to which the speculum was ground — that is, at a distance of five feet and eleven inches from the speculum — in such a manner, that the beam of light might pass through a little hole in the middle of the chart to the speculum, and thence be reflected back to the same hole : I observed upon the chart four or five concentric irises or rings...
Page 1 - Force is that which changes, or tends to change, the state of rest or motion of the body acted upon.
Page 258 - Stokes' suggestion of a mechanical theory has ever appeared in print. I have given it in my lectures regularly for many years, always pointing out along with it that solar and stellar chemistry were to be studied by investigating terrestrial substances giving bright lines in the spectra of artificial flames corresponding to the dark lines of the solar and stellar spectra*.