Objective (optics)

“ The foci of optics are proofs of the illusion of what is termed material sense, as when sky and tree-tops appear to join hands, and clouds and ocean to meet and mingle, when they are as remote at the farther as at the nearer point of vision. ”

“ Thus, that there should be eyes capable of seeing, the laws of optics must be satisfied, reflection, refraction and the rest, just as exactly in the making of an eye as in that of a telescope. De facto they are satisfied. ”

“ The pencil of light is not only turned aside, but it is also widened out into a band which is truly painted with all the colours of the rainbow, every tone and hue being of the most marvellous brilliancy. This long coloured stripe, which constitutes one of the most beautiful sights that the science of optics can afford us, is known to scientific men by the name of the solar spectrum. ”

“ Every one has, doubtless, at one period of his life, amused himself with blowing soap-bubbles by means of a tobacco-pipe and a little lather—a sufficiently childish amusement, you will possibly say, but one narrowly connected with the most intricate secrets of the science of optics. ”

“ The point is, can we make a better one or must we be content with patching up the old one? Take an illustration. Scientists tell us that from the point of view of optics the human eye is a clumsy instrument poorly contrived for its work. ”

“ Of all the senses none is more frequently the seat of such deceptive judgments than that of sight; and in the science of physiological optics a very considerable share of attention is claimed by optical illusions. For the purposes of convenience, we may draw a distinction between these illusions, which are the direct result of certain properties or imperfections of the eye as an optical instrument, and those which arise from obliquities of judgment in interpreting the sensations optically impressed upon the retina of the eye. ”

“ No person, for example, that knows the principles of optics, and the structure of the eye, can believe that it was formed without skill in that science; or that the ear was formed, without the knowledge of sounds:”—“All our accounts of nature are full of instances of this kind. The admirable and beautiful order of things, for final causes, exalt our idea of the Contriver: the unity of design shews him to be One. ”

“ I appeal to anyone's experience, whether he be conscious to himself that he thinks on the intersection made by the radious [SIC] pencils, or pursues the impulses they give in right lines, whenever he perceives by sight the position of any object? To me it seems evident that crossing and tracing of the rays is never thought on by children, idiots, or in truth by any other, save only those who have applied themselves to the study of optics. ”

“ One who never saw the light, may be learned and knowing in every science, even in optics; and may make discoveries in every branch of philosophy. He may understand as much as another man, not only of the order, distances, and motions of the heavenly bodies; but of the nature of light, and of the laws of the reflection and refraction of its rays. He may understand distinctly, how those laws produce the phenomena of the rainbow, the prism, the camera obscura, and the magic lanthorn, and all the powers of the microscope and telescope. ”

“ Comparative sight is a far more important question than comparative anatomy. It is no matter, though we sometimes walk—and it may often be desirable to climb—like apes; but suppose we only see like apes, or like lower creatures? I can tell you, the science of optics is an essential one to us; for exactly according to these infinitely grotesque directions and multiplications of instrument you have correspondent, not only intellectual but moral, faculty in the soul of the creatures. Literally, if the eye be pure, the body is pure ”

“ To a man unacquainted with the principles of optics, almost every experiment that is made with the prism, with the magic lantern, with the telescope, with the microscope, seems to produce some fallacy in vision. Even the appearance of a common mirror, to one altogether unacquainted with the effects of it, would seem most remarkably fallacious. For how can a man be more imposed upon, than in seeing that before him which is really behind him? ”

“ An optical illusion.
courage to get up and go and place yourself in the position which appears to be occupied by the spectre, in order to demonstrate to yourself positively that it is only a vision? ”

“ As truth is single, and consistent with itself, a principle may be as completely and as plainly elucidated by the most familiar and simple fact, as by the most imposing and uncommon phenomenon. The colours which glitter on a soap-bubble are the immediate consequence of a principle the most important from the variety of phenomena it explains, and the most beautiful, from its simplicity and compendious neatness, in the whole science of optics. ”

“ More acute observers would see that something more than mere invention had been at work, and would suppose that the drawings had been the result of marvellously careful induction, made by comparing the phenomena observed in the dead eye with the symptoms of living patients. At last, in the new civilization, someone living outside the tempest of rival theories, and studying optics for himself, would re-discover the principle of the ophthalmoscope, make one, and actually see living retinas. ”

“ Let the eye be kept steadily in one place, and take a distinct view of the object. We know, from the principles of optics, that the rays from any one point of this object, whether they pass through the centre of the eye, or at any distance from the centre which the breadth of the pupil will permit, do all unite again in one point of the retina. ”

“ In order to illustrate the meaning of still further, we use an analogy from optics, namely the relation between image and object. From the pure optical standpoint, object and image are interchangeable. ”

“ It is not necessary to be thoroughly acquainted with the science of optics in order to see. A man may look through a telescope before he can define the refraction or reflection of light. Now all that is included in the word salvation hangs on this simple condition. ”

“ He treats particularly the problem of optics, and physiological optics is the study of perception by means of the sense of sight. We see things in the external world through the medium of light which they direct upon our eyes. The light strikes the retina, and causes a sensation. The sensation brought to the brain by means of the optic nerve becomes the condition of the representation in consciousness of certain objects distributed in space.... ”

“ The majority of those who have written touching the various parts of Optics have contented themselves with presuming these truths. But some, more inquiring, have desired to investigate the origin and the causes, considering these to be in themselves wonderful effects of Nature. ”

“ Optics certainly appertain to the most important and completest branch of physics, and yet the undulatory theory of light, which we accept now as the indispensable basis of optics, rests on an unproved hypothesis, on the subjective assumption of an ethereal medium, whose existence no one is in a position to prove objectively in any way. ”

“ A great philosopher calls the eyes the windows of the soul, and, although meant as a poetical image, the saying is not far from the truth; for the optic nerve by which we see external objects, is an extension of the nerves of the brain, whose functions and actions are an unfathomable mystery. ”

“ The peculiar appearances known as spectres in optics are certain illusions of vision in which an object is apparently presented to the view which does not really exist. In such cases either the brain, the retina, or the optic nerve are unnaturally excited, and made sensitive to an appearance that, physically speaking, does not exist. There is such a close connexion between the senses and the mind, that we continually, and without knowing it, transfer to the physical world that which belongs to the domain of thought. ”

“ They are: 'optical refraction', 'light-ray', and 'light-velocity' - the latter two serving to explain the first. In a science of optics which seeks its foundation in the intercourse between man's own visual activity and the doings and sufferings of light, these three concepts must needs undergo a decisive change, both in their meaning and in their value for the description of the relevant optical phenomena. For they are all purely kinematic concepts typical of the onlooker-way of conceiving things - concepts, that is, to which nothing corresponds in the realm of the actual phenomena. ”

“ It is with our own organization that we shall commence our task of exposing the illusions that we shall meet with during our optical experiments,—in fact with that wonderful and important organ of our body that we are apt to look upon as sure and infallible, but which we shall find is deceiving us constantly, and hourly proving the fallacy of the popular saying, that "every one must believe his own eyes." ”

“ And every one has felt, I should think, the magical transformation, suggestive of looking through another man’s eye and mind, which occurs when you put your eye to the eye-piece of an optical instrument. The outside world of other objects, the tube, the stage, the mirror, the bystanders, the external light, all disappear, and you see nothing but the field of vision and whatever distinctly pictured structure may be displayed within it. The observer who looks through the tube may be compared with each one of us as he contemplates his own world of knowledge and perception. ”

“ Let us now examine the effects of light reflected from plane surfaces. We must first, however, notice a certain optical illusion to which we are continually falling a prey, almost without our knowledge. ”

“ Op′tic (Pope) , an organ of sight: an eye.—adv. Op′tically.—ns. Optic′ian, one skilled in optics: one who makes or sells optical instruments; Op′tics (sing.) , the science of the nature and laws of vision and light; Optim′eter, Optom′eter, an instrument for measuring the refractive powers of the eye; Optom′etry, the measurement of the visual powers.—Optic axis, the axis of the eye—that is, a line going through the middle of the pupil and the centre of the eye. ”

“ This shows once again that the physical optics are the reverse of the imaginary; for, as by physics distant objects seem to us small, so by imagination small objects, the further off they are, seem the larger. ”

“ The beginning of optics [6] will be to look up at the light, a thing natural to children; for the instant it becomes visible, they turn their eyes to it. They must, however, be watched, and not be permitted to look with fixed eyes on excessive light and brilliance, strongly affecting the power of vision, especially at first, lest that power be weakened, or extinguished by overstraining. Let them have the means of seeing moderate light, especially of a green color, and gradually anything that shines. ”

“ Suffice it to note how measureless the superiority, as a mere piece of mechanism, of an average eye to the finest of telescopes, and how just, nevertheless, is the telescope-maker's claim to praise for skilful adaptation to the laws of optics, when he has succeeded in a faint and feeble imitation of some minor part of nature's visual apparatus. ”

“ This confused appearance of the OBJECT doth therefore seem to be the MEDIUM whereby the mind judgeth of distance in those cases wherein the most approved writers of optics will have it judge by the different divergency with which the rays flowing from the radiating point fall on the PUPIL. No man, I believe, will pretend to see or feel those imaginary angles that the rays are supposed to form according to their various inclinations on his eye. ”

“ Nor will this appear very strange, if we consider, that, to make the observations which are necessary for determining these questions, knowledge of the principles of optics, and of the laws of vision, must concur with opportunities rarely to be met with.
Of those who squint, the far greater part have no distinct vision with one eye. When this is the case, it is impossible and indeed of no importance, to determine the situation of the corresponding points. When both eyes are good, they commonly differ so much in their direction, that the same object cannot be seen by both at the same time ”

“ We shall, therefore, in the present chapter, speak of an ingenious instrument which serves to show in relief the images of objects depicted on a flat surface. We have already seen, that although we have two eyes, provided with lenses and screens by means of which the images of things around us are formed, we only perceive a single object; and the student has no doubt long since wondered why nature has bestowed two eyes upon us, when only one would have apparently served the same purpose. ”

“ By means of light we can appreciate the beauties of hue and form, and by its power we touch as it were the inaccessible. It constitutes the most intimate connexion between ourselves and external objects—a connexion that seems even to alter our temper, disposition, and character, according to the variations of its intensity. ”

“ The object of this work is "to treat theoretical optics in a complete and uniform manner on the new foundation of the simultaneous vibration of etherial and ponderable particles, and to substitute a consistent and systematic new structure for the present conglomerate of more or less disconnected principles." Such a work demands a critical examination, which should not be undertaken from any narrow point of view. Any faults of detail will be readily forgiven, if the author shall give the theory of optics the πού στώ which it has sought so long in vain. ”

“ Everybody must have noticed that in order to see objects plainly that are placed at different distances we insensibly alter the position and focus of the eyes, and that, consequently, objects even in the same plane as those we are looking at are not perceived by us until something calls our attention to them, and causes us to alter the position and focus of our eyes and fix our gaze on them. ”