Condenser (optics)

“ Also the space between the components should be well ventilated, in order to provide for the escape of moisture which usually at the start of a lantern exhibition is deposited upon the glass, and should be got rid of before the actual lecture commences.
Even with all care, the back component of a condenser will sometimes crack, though such an accident should be a rare occurrence; and hence a professional operator will usually provide himself with a spare lens, and the condenser should be so constructed that it can readily be changed, and with as little delay as possible. ”

“ That is, the light condenser, the device that stored the photons so close to each other, would also serve to urge them apart. I've made the necessary changes, and now I'm trying to set up the apparatus to work on solid light-mat [Pg. 199] ter. It was developed for gaseous material, and it's a rather tricky thing to change it over. But I think we've almost got it.
“Wade, will you connect that to the high frequency oscillator there—no—through that counterbalanced condenser. We may have to change the oscillator frequency quite a bit, but a variable condenser will do that. ”

“ In our own practice we always place a diffusing screen of very finely-ground glass in front of the condenser at E.E. The diameter of the condenser is governed by the size of the negatives to be enlarged, it must be of sufficient size to include the longer sides of the plate within its circumference without cutting the corners. If it is much larger than this, an unnecessary loss of light will occur, because only that which passes through the negative can be utilized. ”

“ For moderate powers, as a four-tenth or one-fifth, the condenser should be used a little below the focus to give an even illumination over the whole field. Moreover, as to the use of the condenser for defining general objects, it must be borne in mind that to show different kinds of structure different apertures in the iris diaphragm are necessary, and that whereas some objects show their structure better with a large angle of light cut down in intensity by the use of blue glass, others show better with a small pencil of direct rays. ”

“ On removing one condenser after another from the circuit, the lamp is found to glow less and less, till when but one condenser is left, no glowing is observed, since one small condenser does not have sufficient capacity. ”

“ If, as is often the case, the lantern is fitted with several objectives of different foci, it is usually necessary to supply alternative condensers also, or at least to supply an interchangeable front component.
Fig. 36.—Forms of Condensers.
If the entire condenser is too long in focus, light is lost; if too short, it is impossible to obtain an even disc, as there is invariably a dark patch either in the centre or round the edges.
The mounting of the condenser also varies with different makers ”

“ The next element which we have to consider in the transmitting arrangements is a condenser of some kind for storing the energy which is radiated at intervals. Where a condenser other than the aerial is employed for storing the electric energy which is to be radiated by the aerial, some form of it must be constructed which will withstand high potentials. As the dielectric for such a condenser, only two materials seem to be of any practical use, viz., glass and micanite. ”

“ Work done with the concave mirror can, however, under the most favourable conditions, only be looked upon as a pis aller. The advantages gained by the use of some substage condenser, even the most simple, in conjunction with the plane mirror, or even without any mirror at all, are so manifold that the beginner is strongly urged to provide himself with some form or other of it, and we now proceed to describe the way in which this should be used to produce the best effect. ”

“ For exceptionally accurate work microscope objectives are sometimes used as condenser systems. When using immersion objectives, an immersion condenser must also be used if rays of extreme obliquity are wanted, for, in consequence of the total reflections, rays can only come from the upper plane surface of the condenser, which have not a larger inclination to the axis than about 41°, varying according to the refractive index of the glass. ”

“ A very common focal length of condenser is 61⁄2 inches. There is no very accurate relation necessary between the focal length of condenser and objective. There is considerable difference of opinion on this subject and much of it is induced by the possibility of condenser breakage which is increased [52] by using condensers of short focal length, but in this case, as in many others, the operator must find out by his own experiments. ”

“ As intently looking at strongly illuminated objects is injurious to the sight, the amount of light allowed to pass the diaphragm should be no more than is agreeable, and sufficient to show the object distinctly.
In using the higher powers, the field is much less bright with the use of the same light than in the case of the lower powers; and difficulty is often found in obtaining sufficient light for the distinct vision of the object. The achromatic condenser is of most important service here ”

“ For this purpose, the polariscope prisms should be of large size, and both mounted in revolving settings. The lower prism should also fit into a sub-stage, capable of carrying an achromatic condenser above, in order to properly illuminate the field with any objective above the two-thirds inch. The achromatic condenser itself should consist of at least two combinations of different powers and of wide angular apertures. It is always necessary to employ a condenser of greater power than the objective. ”

“ A small camphine-lamp is employed for the purpose of illuminating the negative, having a good bull’s-eye lens as a condenser, so arranged with its flat side next the lamp that the refracted rays shall just fill the whole of a double convex lens of about six inches in diameter, the latter being placed in such a position as to refract the rays of light in a parallel direction upon the negative. ”

“ Expand slightly by blowing if necessary. If a small pin-hole develops at the joint it is sometimes possible to close this with a bead of hot glass; but if the bulb has been cut properly there should be no pin-holes formed. The condenser is finished by joining on the side tubes and sealing the inner tube through by the methods already given. In order to blow bulbs large enough to make a useful condenser, it will be convenient to employ the multiple-jet blowpipe described on page 4. ”

“ We may here remark that any arrangement of two metallic plates with a sheet of insulator or non-conductor between them is called a condenser. Thus, a condenser can be built up by coating a sheeting of glass on its two sides with tinfoil, or in place of glass we may use mica, paraffin paper, or any other good non-conductor. We may even use air at ordinary pressures; and thus, if two metal plates are placed near to one another in air, the plates being both insulated—that is, supported on non-conductors,—this arrangement constitutes what is called an air condenser. ”

“ If now there be any damping of the electric oscillations, the effect of the one condenser on the polarized ray for, say, the first oscillation, may be made equal to that of the other condenser for the second oscillation by such a rotation, and so on. Thus these two condensers become an equivalent "crossed" system, the one compensating completely the effect of the other, even if the electric stresses in each are not the same. This would hold for electric oscillations which produce successive stresses that are in a constant ratio to each other. ”

“ Transformation of Sound into Light.—M. Trève, a ship captain, has described to the French Academy of Sciences an experiment with the apparatus called the singing condenser, by which he believes that he produces a transformation of sound into light. If we bring the current of a Ruhmkorff coil to bear upon one of these condensers, the latter will repeat on a larger scale the vibratory movement of the coil. The noise which it makes is due to the vibrations of the air in the condenser under the shock of the electric current. ”

“ The frame holding plates can be readily adjusted at the proper polarising angle, the analyser being the ordinary small Nicol, screwed above the objective. The illuminator is an Abbe’s triple condenser, of numerical aperture 1·40, which can be adjusted in the ordinary way. The front lens of this should have a diameter of 11·12 mm. and the lower lens of 30 mm. This increase in the condenser fully compensates for the loss of light by the bundle of glass plates, and also enables thick sections of crystals to be examined in convergent polarised light. The ocular used should have a large field ”

“ Of course, we might make the e. m. f. stronger, that is pull and shove the electrons harder, but unless the coil has a very small inductance or unless the frequency is very low we should have to use an e. m. f. of enormous strength to get any appreciable current.
Condensers are just the other way in their action. If there is a condenser in a circuit, where an alternating e. m. f. is active, there is lots of trouble if the frequency is low. If, however, the frequency is high the same-sized current can be maintained by a smaller e. m. f. than if the frequency is low. ”

“ A is an induction coil, supplied with current from the battery B, and C is a condenser. A condenser is simply an apparatus for storing up charges of electricity. It may take a variety of forms, but in every case it must consist of two conducting layers separated by a non-conducting layer, the latter being called the “dielectric.” The Leyden jar is a condenser, with conducting layers of tinfoil and a dielectric of glass, but the condensers used for wireless purposes generally consist of a number of parallel sheets of metal separated by glass or mica, or in some cases by air only. ”

“ The insulating qualities of air are reduced by heating of the condenser plates and by reductions in the air pressure. If the plates are put in a vacuum, there is practically no dielectric between them.
In speaking of the vanishing metal, I think Kathis Kathkan referred to the light tinfoil in a condenser which is sometimes eaten away by the brushing of too high a voltage. Copper, brass, or aluminum will not eat away like the foil. ”

“ In this case it must be assumed that some such process as conduction through the glass takes place, and all the more as it is possible to show by experiment, that with a sufficiently high steady difference of potential, enough current can be passed through the glass of a condenser with mercury coating to light up a Geissler tube joined in series with the condenser. When the potential is alternating, the condenser action comes in and conduction becomes insignificant, and the more so, the greater the rate of alternation or change per unit of time. ”

“ In this case the wire leading from the outside into the bulb is omitted, the energy required being supplied through condenser coatings C C. The insulating packing P should in this construction be tightly fitting to the glass, and rather wide, or otherwise the discharge might avoid passing through the wire w, which connects the inside condenser coating to the incandescent button m. The molecular bombardment against the glass stem in the bulb is a source of great trouble. As illustration I will cite a phenomenon only too frequently and unwillingly observed. ”

“ Sometimes, for special forms of illumination, it is necessary to cut off some of the rays of light passing through the condenser. It may be that we desire to dispense with the outer rays of the cone of light or, when delicate details are being studied, we may wish to impede the central rays. ”

“ A collective lens of extra light-gathering power is fitted in front as condenser, and from it proceeds a light-tight tube provided with a water cell to filter out most of the heat rays which accompany the light. ”

“ Fixed and Variable Condensers.--You do not require a condenser for a simple receiving set, but if you will connect a fixed condenser across your headphones you will get better results, while a variable condenser connected in the closed circuit of a direct coupled receiving set, that is, one where a double slide tuning coil is used, makes it easy to tune very much more sharply; a variable condenser is absolutely necessary where the circuits are inductively coupled, that is, where a loose coupled tuner is used. ”

“ For micro-photography the following practical rules must be observed. The sub-stage condenser may be dispensed with when low powers are used, as well as the mirror, and the lamp so placed that the image of the flat of the flame appears accurately adjusted in the centre of the field of the microscope. The bull’s-eye lens is so interposed, that the image of the flame disappears, and the whole field becomes equally illuminated with high powers; the sub-stage achromatic condenser must be used, and a greater intensity of illumination is obtained by placing the lamp-flame edgeways. ”

“ Since effective single lenses of large diameter are necessarily of long focus, a really good condenser of considerable diameter and yet of short focus must be a combination of two or more lenses. It is essential that the condenser be white and limpid and free from defects or striae. ”

“ If the upper plate is touched with the finger or connected to earth for a moment, a negative charge will escape from the metal plate to earth at that moment. The arrangement thus constitutes a condenser; the upper plate on its under surface carries a charge of positive electricity and the resin plate a charge of negative electricity on its upper surface, the air film between them being the dielectric of the condenser. If, therefore, the upper plate is elevated, mechanical work has to be done to separate the two electric charges. ”