refractable (refraktabl)

[ refraction (re-frak's hon), F. réfraction = Sp. refraccion = Pg. refracção = It. rifrazione, refrazione, refraction medium the density of which is not uniform, as the atmosphere. It is found (1) that, when pa ing into a denser isotropic medium, the ray is refracted toward the perpendicular to the surface, and bent away from it when pa ing into one le dense; (2) that the sines of the angles of incidence and refraction bear a constant ratio to each other for any two given media; and (3) that the incident ray and the refracted ray are in the same plane. Thus, if (fig. 1) SP represents a ray incident upon the surface of S water at P, it will be bent away from its original direction SPL toward the perpendicular Qq in pa ing into the denser medium, and make an angle qPR, such sin SPQ that the is a constant sin RPq quantity-that is, the perpendicular distance of a point q (such that the line from it to P, the point of incidence, is normal to the surface) from the refracted Q P IRL Fig. 1. path bears a constant ratio to its distance from the path as it would be without refraction, however the angle of incidence varies; but this constant depends on the nature of the two media. If the first medium is air, this constant ratio is called the index of refraction or refractive index of the given substance (or n). Again, if the ray proceeded from R to P, it would be bent away from the perpendicular in the direction PS. The latter case is peculiar, however, in that for a certain angle of incidence called the critical angle (whose sine = 1 / n) the angle of refraction of QPS is a right angle and a ray incident at P at any greater angle cannot pa out into the rarer medium at all, but suffers total reflection at P. In fig. 2, AHC is the angle of incidence, and EHK the angle of refraction, CD being the normal to the surface; if, further, the second surface is parallel to the first, the ray emerging into the original medium at E has a direction EF parallel with its first direction, AH. If (fig. 3) the refracting me F H 9 EK D Fig. 2. A dium has the form of a prism (ABC), the incident ray LF suffers a double change of direction, first (FE) in pa ing into the prism, and second (EG) in emerging from it; the total angle of deviation IDL varies in value with a change in the direction of LF, but has a definite minimum value when the angles of incidence and emergence are equal. If d represents the angle of the prism BAC, and the angle of minimum deviation, LDI, then the refractive index n of the material of which the prism is made is sin (d+r). given by the relation n = The angle of desind viation or refraction also increases as the wave-length of the ray diminishes, and hence a beam of white light in pa ing through a prism is both refracted and dis persed, thus yielding a spectrum. The phenomena of the refraction of light explain the properties of lenses (see lens ) and of prisms (see prism and spectrum ). Sound waves may also be refracted when pa ing from one medium to an other of different density, obeying the same laws as light. Double refraction is the separa I IMG:content-1851.png:[blocks in formation] Section of a Prism, showing the refraction of a transmitted light-ray along the path LF, FE, EG. tion of a ray of light into two rays, which are unequally refracted upon pa ing through an anisotropic medium. This property belongs to all transparent crystalline substances except those of the isometric system. A strik ing example is calcite, hence called doubly refracting spar. In uniaxial crystals (those belonging to the tetragonal and hexagonal systems) one of the rays follows the ordinary law of refraction (see law (2), above), and is called the ordinary ray; the other, which does not, is called the extraordinary ray; both rays are polarized (see polarization ), the ordinary ray having vibrations perpendicular to and the extraordinary ray vibrations parallel to the vertical axis. If the index of refraction is greater for the ordinary ray than for the extraordinary ray, the crystal is said to be negative, and in the opposite case positive: otherwise expre ed, a crystal is negative or positive according as the crystallographic axis (optical axis) is the axis of greatest or of least elasticity. In the direction of the vertical axis a ray suffers no double refraction, and this direction is called the optic axis. In biaxial crystals (those belonging to the orthorhombic, monoclinic, and triclinic systems) neither ray follows the ordinary law of refraction, and there are two directions, called optic axes, lying in the plane of the axes of greatest and least elasticity, in which a ray suffers no double refraction. There are also three indices of refraction, corresponding to the rays propagated by vibrations parallel to the three axes of elasticity. A biaxial crystal is called negative or positive according as the acute bisectrix coincides with the axis of greatest or of least elasticity. According to the degree of difference between the two indices of refraction of a uniaxial crystal and between the greatest and least of the three indices of a biaxial crystal, the double refraction is said to be strong or weak; upon this difference depends the brilliancy of color of thin sections of a crystal as seen in polarized light. Amorphous substances like gla do not show double refraction, except under abnormal conditions, as when subjected to unequal strains, as in gla suddenly cooled. This is also true of crystals be longing to the isometric system, which, however, some show secondary or abnormal double refraction (as garnet), due to internal molecular strain or other cause For the refraction of the eye, see eyel, and crystalline hu mor (under crystalline ). Errors of refraction in the eye are tested by trial with lenses, test types, etc., by the ophthalmoscope, or by skiascopy or the shadow-test, and are corrected by appropriate gla es. especially of metals and the like that require an extraordinary degree of heat to fuse them, or that do not yield readily to the hammer. In metallurgy an ore is said to be refractory when it is with difficulty treated by metallurgical proce es, or when it is not easily reduced. Stone, brick, etc., are refractory when they resist the action of fire without melting, crack ing, or crumbling. Refractory materials are such as can be used for the lining of furnaces and crucibles, and for similar purposes. 3. Not susceptible; not subject; resisting (some influence, as of disease). [Rare.] They sang the refrain :- "The roads should blo om, the roads should bloom, So fair a bride shall leave her home!" Long fellow , Blind Girl of Castèl-Cuillè. 2. The musical phrase or figure to which the burden of a song is set. It has the same relation to the main part of the tune that the burden has to the main text of the song. obstinate in opposition or disobedience. Render not yourself a refractory on the sudden. 2t. Obstinate opposition. Glorying in their scandalous refractories to public order and constitutions. Jer. Taylor (?), Artif. Handsomene , p. 138. 3. In pottery , a piece of ware covered with a vaporable flux and placed in a kiln to communi- cate a glaze to other articles. E. H. Knight . refracture (re-fraktur), n . [ refractory .] 1. A breaking again, as of a badly set bone. -2†. Refractor i- ne ; antagonism. [Rare.] ref rag ability (refra-ga-bil'i-ti), n. [ refragabilita ( t- ) s , refragabilis , refragable:see refragable .] The state or quality of being ref- ragable; ref rag able ne . Bailey . refragable (ref'ra-ga-bl), a . [=Pg. refragavel , n . The char- acter of being refragable. [Rare.] refragatet (ref'ra-gat), (ref' v . i . [ refragatus , pp . of refragari , oppose, resist, contest, gain- say, re- , back, again, + fragari , perhaps frangere ( ✓ frag ), break: see fragile .] To op- refractorine (re-frak'tō-ri-nes), n. The state or character of being refractory, in any sense. refractory (rē-frak'tō-ri), a. and n. [Errone- ously for the earlier refractary , refractarius , stubborn, obstinate, refractory: see refractary . ] I. a . 1. Resisting; unyielding; sullen or per- verse in opposition or disobedience; obstinate in non-compliance; stubborn and unmanage- able. There is a law in each well-order'd nation To curb those raging appetites that are Most disobedient and refractory . refrain1 (re-fran'), v . [Early mod. E. refrayne , refreyne, refreinen , refreynen, refraynen, refraindre , refreindre , also refrener , F. re- fréner , bridle, restrain, repre , = Pr. Sp. re- frenar = Pg. refrear = It. raff ren are , frenare , bridle, hold in with a bit, L.re- , back, + frenum , frænum , a bit, curb, pl. frena , curb and reins, a bridle: see frenum .] I. trans. 1. To hold back; restrain; curb; keep from ac- tion. freinor ; refrain1 + -er1 .] One who refrains. So these ii. persons were euer cohibetors and refreinors of the kinges wilfull skope and vnbrideled libertie. Hall , Hen. VII., an. 18. refrainingt (rē-fra'ning), n. [ refrain- ing , the singing of the burden of a song; verbal n. of * refrain2 , v., refrener , sing a refrain, refraindre , repeat, sing a song: see refrain2 .] The singing of the burden of a song. She couthe make in song sich refreynynge, It sat [became] hir wonder wel to synge. Bunyan , Pilgrim's Progre , p. 84. Ps. lxxvi. 10 (Psalter). 2t. To forbear; abstain from; quit. Men may also refreyne venial sinne by receyvynge worthily of the precious body of Jhesu Crist. At length, when the sun waxed low, Then all the whole train the grove did refrain , And unto their caves they did go. Washington , quoted in Bancroft's Hist. Const., I. 282. II. in trans . To forbear; abstain; keep one's self from action or interference. Dread full of daunger that mote him betyde, She oft and oft adviz'd him to refraine From chase of greater beastes. Spenser , F. Q., III. i. 37. Acts v. 38. The chat, the nuthatch, and the jay are still; The robin too refrains . IMG:content-1852.png:[blocks in formation] The Century Dictionary and Cyclopedia 5040 refrigeration refresh (re-fresh'), v. (re-fresh), [ = It . rinfrescare , ref res care , refriscare ), refresh, cool, re- , again, + friscus , frescus , new, recent, fresh: see fresh .] I. trans . 1. Το make fresh or as if new again; freshen; improve; restore; repair; renovate. I have desirid hym to move the Counsell for refreshing of the toun of Yermowth with stuff of ordnance and gonnes and gonne powdre, and he seid he wolde. Paston Letters , I. 427. Before I entered on my voyage, I took care to refresh my memory among the cla ic authors. Add is on , Remarks on Italy, Pref. I remember, old gentleman, how often you went home in a day to refresh your countenance and dre when Teraminta reigned in your heart. Steele, Tatler, No. 95. As in some solitude the summer rill Refreshes, where it winds, the faded green. Cowper , In Memory of John Thornton. 2. To make fresh or vigorous again; restore vigor or energy to; give new strength to; reinvigorate; recreate or revive after fatigue, privation, pain, or the like; reanimate. I am glad of the coming of Step han as and For tun at us, for they have refreshed my spirit and yours. 1 Cor. xvi. 17, 18. And labour shall refresh itself with hope, To do your grace ince ant services. Shak ., Hen. V., ii. 2. 37. There are two causes by the influence of which memory may be refreshed , and by that means rendered, at the time of deposition, more vivid than, by reason of the joint influence of the importance of the fact and the ancientne of it, it would otherwise be. One is intermediate statements. Another is fresh incidents. Bentham , Judicial Evidence, i. 10. 3. To steep and soak, particularly vegetables, in pure water with a view to restore their fresh appearance.=Syn. 1 and 2. To revive, renew, recruit, recreate, enliven, cheer. II. in trans . 1. To become fresh or vigorous again; revive; become reanimated or reinvigorated. I went to visite Dr. Ten is on at Kensington, whither he was retired to refresh after he had ben sick of the smallpox. Evelyn , Diary, March 7, 1684. 2. To take refreshment, as food or drink. [Colloq.] Tumblers refreshing during the ce ation of their perThackeray, Vanity Fair, Ixvi. formances. 3. To lay in a fresh stock of provisions. [Colloq.] We met an American whaler going in to refresh . Simmond's Colonial Mag. (Imp. Dict.) refresht (re-fresh'), n. [ refresh , v .] The act of refreshing; refreshment. Beauty, sweete love, is like the morning dew, Whose short refresh upon the tender green Cheers for a time. Daniel , Sonnets, xlvii. refreshen (rē-fresh'n), v. t. [ Sir J. Reynolds, On Du Fresnoy's Art of Painting, Note 28. It had begun to rain, the clouds emptying themselves in bulk to animate and refreshen the people. S. Judd , Margaret, i. 13. refresher (rē-fresh'ér), n . 1. One who or that which refreshes, revives, or invigorates; that which refreshes the memory. This [swimming] is the purest exercise of health, The kind refresher of the summer heats. Thomson, Summer, 1. 1258. Every fortnight or so I took care that he should receive a refresher, as lawyers call it a new and revised brief memorialising my pretensions. De Quincey , Sketches, I. 72. (Davies.) Mi Peecher [a schoolmistre ] went into her little official residence, and took a refresher of the principal rivers and mountains of the world. Dickens , Our Mutual Friend, ii. 1. 2. A fee paid to counsel for continuing attention or readine , for the purpose of refreshing his memory as to the facts of a case before him, in the intervals of busine , especially when the case is adjourned. [Colloq., Eng.] Had he gone to the bar, he might have attained to the dignity of the Bench, after feathering his nest comfortably with retainers and refreshers. Fortnightly Rev. , N. S., XL. 28. refreshful (rē-fresh'ful), a . [ They spread the breathing harvest to the sun, That throws refreshful round a rural smell. Thomson, Summer, 1. 364. Refreshfully There came upon my face. Dew-drops. Keats , Endymion, i.