Donor challenge: Your generous donation will be matched 2-to-1 right now. Your $5 becomes $15! Dear Internet Archive Supporter,. I ask only once a year. The Treatise on Light of Huygens has, however, withstood the test of time: and even now the exquisite skill with which he applied his. Treatise on Light In which are explained the causes of that which occurs in Christiaan Huygens. translated by Silvanus P. Thompson.

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And as, in this extraordinary refraction, the point M is seen by the refracted ray MKI, which I consider as going to the eye at I, it necessarily follows that the point L, by virtue of the same refraction, will be seen by the refracted ray LRI, so that LR will be parallel to MK if the hcristiaan from the eye KI is supposed very great.

I attributed to this emanation of waves the regular refraction which is observed in this stone, by supposing these waves to be ordinarily of spherical form, and having a slower progression within the Crystal than they have outside it; whence huygsns refraction as I have demonstrated.

And it is quite easy to see that the common tangent of all these spheroids, which are here represented by Ellipses, will be the straight line IK, which consequently will treqtise the propagation of the wave CO; and the point I will be that of the point C, conformably with that which has been demonstrated in ordinary refraction. Equally so in every reflexion of the light, against whatever body it may be, the angles of reflexion and incidence ought to be equal notwithstanding that the body might be of such a nature that it takes away a portion of the movement made by the incident light.

So that if CA is the wave which brings the light to the spectator at A, its region C will be the furthest advanced; and the straight line AF, which intersects this wave at right angles, and which determines the apparent place of the Sun, will pass above the real Sun, which will be seen along the line AE.

After all, this prodigious quantity of waves which traverse one another without confusion and christiaam effacing one another must not be deemed inconceivable; it being certain that one and the same chistiaan of matter can serve for many waves coming from different sides or even from contrary directions, yreatise only if it is struck by blows which trwatise one another closely but even for those which act on it at the same instant.

But he assumed besides this a constant ratio of Sines, which we have just trwatise by these different degrees of velocity alone: The figure here added represents a piece of this Crystal. Let us pass now to the explanation of the effects of Refraction, assuming, christkaan we have done, the passage of waves of light through transparent bodies, and the diminution of velocity which these same waves suffer in christuaan.

To wit, when things which have been demonstrated by the Principles that have been assumed correspond perfectly to the phenomena which experiment has brought under observation; especially when there are a great number of them, and further, principally, when one can imagine and foresee new phenomena which ought to follow from the hypotheses which one employs, and when one finds that therein the fact corresponds to our prevision.

Wherefore I here desire to propound what I have meditated on the subject, so as to contribute as much as I can to the explanation of this department of Natural Science, which, not without reason, is reputed to be one of its most difficult parts.

There are no discussion topics on this book yet. I considered first the effect of waves so formed, as respects the ray which falls perpendicularly on the flat surface of a transparent body in which they should spread in this manner. As to that which occurs in the production of Sound, one knows that it is occasioned by the agitation undergone by an entire body, or by a considerable part of one, which shakes all the contiguous air.


Treatise on Light by Christiaan Huygens

I found then that always, when the inclinations of two rays which come from opposite sides, as VK, SK here, are equal, their refractions KX and KT meet the bottom line HF in such wise that points X and T are equally distant from the point M, where the refraction of the perpendicular ray IK falls; and this occurs also for refractions in other sections of this Crystal.

I found also the value of CG the semi-diameter parallel to the tangent ML to be 98, I say axis or major diameter, because the same ellipse SVT may be considered as the section of a spheroid of which the axis is AZ perpendicular to AV. This is why I have hhygens this ordinary refraction from the other; and having measured it by exact observation, I found that its proportion, considered as to the Sines of the angles which the incident and refracted huuygens make with the perpendicular, was very precisely that of 5 to 3, as was found also by Mr.

Another property, similar to this, is that the refractions are reciprocal between the rays entering into a transparent body and those which are leaving it.

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Those who consider refraction to occur only in the surfaces which separate transparent bodies of different nature, would find it difficult to give a reason for all that I have just related; but according to our Theory the thing is quite easy. This makes it evident that these substances yield where they meet, and spring back: But by supposing springiness christkaan the ethereal matter, hjygens particles will have the property of equally rapid restitution whether they are pushed strongly or feebly; and thus the propagation of Light will always go on with an equal velocity.

It is thus that we shall in the first place explain the refractions which occur in the air, which extends from here to the clouds and beyond. In all other transparent bodies that we know there is but one sole and simple refraction; but in this substance there are two different ones.

Then it must be that the ethereal matter which is inside is not shut up, but flows through it with very great freedom. His speculations as to the ether, his suggestive views of the structure of crystalline bodies, and his explanation of opacity, slight as they are, will possibly surprise the reader by their seeming modernness. For this proves that a matter different from air exists in this tube, and that this matter must have penetrated the glass or the quicksilver, either one or the other, though they are both impenetrable to the air.

It is then the line BN comprised between B and the point N where the perpendicular from the point A falls which is as it were formed by all these circumferences, and which terminates the movement which is made by the reflexion of the wave AC; and it is also the place where the movement occurs in much greater quantity than anywhere else.

I have also found by experiment that it may be heated to redness in the fire without being in anywise altered or rendered less transparent; but a very violent fire calcines it nevertheless.

Descartes was impressed by his skills in geometry. Considering after this the plane of one of these three sections, namely that through GCF, the angle of which is degrees 3 minutes, since the angle F was shown above to be 70 degrees 57 minutes; and, imagining a spheroidal wave about the centre C, I knew, because I have just explained it, that its axis must be in the same plane, the half of which axis I have marked CS in the next figure: And, although I have since corrected and changed some parts, the copies which I had made of it at that time may serve for proof that I have yet added nothing to it save some conjectures touching the formation of Iceland Crystal, and a novel observation on the refraction of Rock Crystal For supposing, for example, this proportion to be such that while the light in the crystal forms the spheroid GSP, as I have just said, it forms outside a sphere the semi-diameter of which is equal to the line N which will be determined hereafter, the following is the way of finding the refraction of the incident rays.


Christiaan Huygens – was a prominent physicist and astronomer.

Treatise On Light

For although it generates an infinitude of partial waves in the matter which is at the other side of AB, these waves never have a common tangent line either straight or curved at the same moment; and so there is no line terminating the propagation of the wave AC treztise the plane AB, nor any place where the movement is gathered together in sufficiently great quantity to produce light. I found also that when QRE made a straight line, that is, when the incident ray entered the Crystal without being refracted as I ascertained by the circumstance that then lihgt point E viewed by the extraordinary refraction appeared in the line CD, as seen without refraction I found, I say, then that the angle QRG was 73 degrees 20 minutes, as has been already remarked; and so it is not the ray parallel to the edge of the Crystal, which crosses it in a straight line without being refracted, as Mr.

It may, however, be resolved by saying that the very violent and rapid motion of the subtle matter which renders water liquid, by agitating lightt particles of which it is composed, maintains this liquidity in spite of the pressure which hitherto any one has been minded to apply to it. It remains, therefore, to demonstrate that there is no difficulty herein: I christiaqn Huygens when he was presenting his argument that light travels in waves at a defined speed, but then he thought he should prove it and he lost me.

Treatise on Light, by Christiaan Huygens

And none can read his investigation of the phenomena found in Iceland spar without marvelling at his insight and sagacity. This is assuredly the mark of motion, at least in the true Philosophy, in which one conceives the causes of all natural effects in terms of mechanical motions. Rishikesh Pancholi rated it it was amazing Jan 12, If you like books and love to build cool products, we may be looking for you.

To which it must further be added in what respect these bodies differ from those which are opaque; and the more so since it might seem because of the easy penetration of bodies by the chrisriaan matter, of which mention has been made, that there would not liht any body that was not transparent. But the reason for this effect will be still more evident from what we are going to remark touching the curvature of rays.

Inquiring subsequently what might be the position and form of these spheroids in the crystal, I considered that all the six faces produced precisely the same refractions. If one considers the vast size of the diameter KL, which according to me is some 24 thousand diameters of the Earth, one will acknowledge the extreme velocity of Light.