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PHY4 - L GHT WAVES AN OPTICS ELECTROMAGNETIC WAVES Light...

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Unformatted text preview: L GHT WAVES AN OPTICS ELECTROMAGNETIC WAVES Light waves are a special me oftransveroe traveling wave called electromagnetic waver, which are produced by mutually inducing oscillations of electric and magnetic fields. Unlike other waves, they do not need a medium, and can travel in avacuum ataspeed of c = 3.00 x 105 mfs. ' Electromagnetic spectrum: Eleononmgnefic waves are distinguished by their frequencies (equivalently, their wavelengths). We can list all the difierenr kinds ofwaves in order. - 'Iheorder ofoolors in the spectrum ofvisiblelight can be remembered with the mnemonic My 6. Bio. DISPERSION DIsporsIon is the breaking up ofvisible light into its compo- nent frequencies. - A prism will disperse light because of a slight difference in refraction indioesfor light oldit- ferent frequencimr: and < nuclei,- “is DIFFRACTIDN Light bends around obstacles slightly: the smaller the aper- ture, the more notioeable the bending. - Wong's blob-flit W demonstrates the wave—like OPTICAL INSTRUMENTS. MIRRIJRS AND LENSES Lenses and curved minors are designed to change the direc- tion o‘l'light rays in predictable ways humane ofrefraction (lenses) or reflection (mirrors). . Com mirrors and lenses bulge outward; concave ones, like caves, curve inward. Center of curvatur- EC‘): Center of the lappmximatEJ l sphere ofwhich the mirror orlens surfaoeis a slice. The l radius (r) is called the radius oi curvature. Principe! atria: lmag'nary line ruimingthrough the center. Wm: Intersection ofprinoipal arciswith mirror or terms} Foaal point (F): Rays of light running parallel to thei l l l l l . behavioroflight: Iflight orfasin- ge wavdengah A is allowed to passthraughtwonnallsijtsadis— tanmdaparhdrenlheimagenna screen adistatmLawaywilbea _ series of altemeting bright and d1 dalr hinges, with the brightest fringein lhemiddle. 0 More precisely, point .P on the screen willbethecenher ofa bright fringeifthelinemnnedingP with the point halfway bdwoenthetw) fr slits and the horizontal malre an angleofd'suththatdsinfi : M,uhmenh anyintemr. Point P will be the center of a dark fringe if daind = (n+ %) A. whereas is again aninteger. A single oil will also produce a briglttfdark fringe pat- tern, though much less pronounced: the central band is larger and brighter; the other bands are less no’dmble. The formulas for which points are bright and which are dark arethe same; this lime, let d be the width ofthe slit. principal axis will be reflected or refracted through lhel same focal point. The local length (f) is the distancel between the vertexand the focal] point. For spherical mir- rors, thefocallength is halfthe radius oforrvature: f = E. An image is real filight rays actually hit its location. Otherwise, the image is v'l'luab it is permitted only. Ray hating techniques 1. Rays running parallel to the principal axis are reflected or refracted toward orawayfmm the focal point (toward F in concave mirrors and convex lenses; away from Fin , convert mirrors and concave lenses). . Conversely, rays running through the focus are reflected or refracted parallel to the principal axis. . The normal to the vertex is the principal axis. Rays run, ning through the vertex ofa lens do not bend. . Concave mirrors and lenses use the near focal point; convex mirrors and lenses use the far focal point. . Images formed in front of a mirror are real; images fDI'ITIBfl behind a minor are virtual. Images formed in front ofa lens are virtual; images formed behind are real, 1 : mooncv In Hi: to? n’ no“ I 'n-‘ "1-! kmhngthlinml IE ”all 1=7mnm vlslalo Iflrl 360nm REFLECTION AND REFRACTIDN At the boundary of one medium with another, part ofthe incident ray oflight will be reflected. and part will be trans- mitlud but retract-d. - All angles [of incidence, reflection, and refraction) are measured from the nor- mal (perpendicular) to the boundary surface. Law of reflection: The angle of relimtion equals the angle of inm'dence. Index of rufradion: Ratio of the speed of light in a vacuum to the speed of light in a medium: in : é, in general, the (laser the substance, the higher the index of refraction. Sn-ll't Low: If a light ray travels from a medium with index of refracbon :11 at angle of incidence 91 into a medium with index of refraction 733 at angle of refrac- tion 92, then r l l l l l l l l l l LENSES AND CURVES MIRRORS imse ' Formulas, obiad; 5 Optical instrument Focal distance r Image distance a Type of image positive (same side} negative [opposite side) in sinfl. = m sin 92. “Sail“? (”13130539 Side} Light passing into a denser medium will hand toward the normal; into a less dense medium. away from the normal. Total ‘lrternal redaction: A light ray traveling from a denser into a less dense medium (111 > 73:] will expert enoe total internal reflection (no light is transmitted] if the angle ofinm'denoe is greater than the critical origin, which is given by _ ‘ ER. 9c—au'csmnl. THERMODYNAMICS TE RMS AN D DE FIN ITICINS 2. Convection: Method ofheat transferin a gas or liquid in Carnotlhoourn:Noengine workingbetween two heat reser- It to the I I In eti which hot fluid rises through cooler fluid. Wire is more efficient than a reversible engine. The effi- d::°ys:mno:‘:s:|::¢ average mo ecu at a General 3. Radiation: Method of heat; hairsfer that does not need a oiencyofa Comet angina is given by 5,: = l — 5:. medium: the heat enery is retried in an electromagnetic me. _ Ideal gas law: PV : refill", where n is the number of moles AWE OF THERMODYNAMICS of the gas, T is the absolute temperature [in Kelvin), and “A I‘m“ "W '3' M““’"'“““= 1‘ “"0 Systems ““3 i" R = 3.314 Jainism) is the universal gas constant. thermal equilibrium with a third, than they are in thatL mal equilibrium with earth other. . First Law ofThormodynarrios: The change in the internal enery ofa system U plus the work done bythe system W equals the not heat Q added to the system: Q = AU + W. 2. Second Law of Modynamios (three formulations]: . Heat flows spontaneously from a hotter object Ina a cooler one, but not in the opposite direction. . No machine can work with 100% efficiency: all machines generate hear, some of which is lost to the surroundings. 3. Any system tends spontaneously onwards maximum positive (opposite side) negative (same side) negative (same side) Heat is the transfer of themal energy to a system via ther- mal contact with a reservoir. Heat malty of a substance is the heat energy required to raise the temperatureofthat submarine try 1° Celsius. 0 Hard energy (Q) is related tothe heat capacitth) by the relation Q : CAT. Substances exist in one of three states (solid, liquid, get]. When a substance is undergoing a physical change of state referred to as a phase change: - Solid to liquid: mall's-lg, fusion, liquefaction Liquid to solid: freezing. solldiIioo‘llon Liquid to gas: vaporization Gas to liquid: condensation Solid to gas (directly): sublimation Gas to solid (directly); deposition Entropy (S) is a measure ufthe disorderofa system. THREE METHDDS CIF HEAT TRANSFER 1. Conduction: Method of heat transfer through physical contact. The ideal gas law incorporates the [allowing gas laws (the amount of gas is Instant for each one): - Charles“ Law: % = £1 ifttre volume is constant. U Boyle's Law: P114 = Pal/2 ifthe temperatureis mnatant. Mlational lrlnotle energy for ideal gas: N(KE) = mime)” = gNrr = gum", where N is the number of molecules is : 1.381 x 10’23 JfK is Boltzmann’s constant. and won dor Woods equation for ml goons: (Pug) (V—im):rrRT Here, b accounts for the correction due the volume of the molearle-i and a amt-its [hr the attraction nt'the gas mole eoulos to each other. This downloadable PDF copyright © 2004 by SparkNotes LLC. SPARKCl—IARTE '1 ...
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