GO Quantum Versi Indo

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Interaksi Cahaya danMateri (2)Sifat cahaya pada tingkat atom (at the atomic level)Penjelasan tentang interaksi cahaya denganmateriTeori Gelombang tidak dapat menjelaskanfenomena fisika pada tingkat atau skala atomikcontoh pada efek fotolistrik ( the photoelectric effect)Page 127Emitter Plate (Cathode)Collector Plate (Anode)Elektrondipancarkan dariplat logamAliran ArusEfek FotolistrikCahaya dipancarkanke katoda yang terbuat dari logamdalam tabungvakummenyebabkanelektron-elektronterlepas dan pergimenuju anoda Arus mengalirdalam rangkaianVACUUM TUBEAmmeter+Efek Fotolistrik Teori Gelombang Menerangkan bahwa:a) Energi yang terkumpul dari cahaya yang diserap logamakan menyebabkan elektron terlepas (sunbathing effect)b) Setiap panjang gelombang dari cahaya akan menghasilkanemisi terpicu/stimulasi elektron selagi energi total yang datang ke logam cukup. c) Semakin kuat energi cahaya yang datang, semakin besarenergi yang dipunyai elektron yang terlepas. (a) Energi yang terkumpul dari cahaya yang diserap logamakan menyebabkan elektron terlepas (sunbathing effect)Efek Fotolistrik(c) Semakin kuat energi cahaya yang datang, semakin besarenergi yang dipunyai elektron yang terlepas. Teori Kuantum membuktikan bahwa terori gelombang salah:Elektron terlepas secara instant selagi energi fotonyang datang melebihi energi ikat elektron dengan intiHanya panjang gelombang cahaya dengan energi > dari energi ikat yang dapat melepaskan elektronEnergi Kinnetik dari elektron yang terlepas tidakbergantung pada Intensitas cahaya yang datang(b) Setiap panjang gelombang dari cahaya akanmenghasilkan emisi terpicu/stimulasi elektron selagienergi total yang datang ke logam cukup. Tingkat Energi Atom:(yang tidak bisa dijelaskan dengan TeoriGelombang)Pada Tingkat atom, cahaya digambarkansebagai paket-paket energi (foton)Setiap foton mempunyai tingkat tingkatenergi yang diskrit. Elektron yang mengorbit inti atom berada padatingkat-tingkat energi yang diskrit.E=energy per photonh=Plancks constant (6.62 10-34 joule sec)=photon frequencyc=velocity of light in a vacuum=photon wavelengthEnergi Fotonc hh E= =Frekuensi (Panjang Gelombang) vs. Energi Fotonjoulesc hh Enm Green1998 3410 38 . 310 6 . 58710 3 10 62 . 6: ) 6 . 587 ( = == = Perbandingan energi yang dibawa oleh foton cahayahijau (Green - 587.6 nm) dan foton dari cahaya biru(Blue - 400 nm) :joulesc hh Enm Blue1998 3410 97 . 410 40010 3 10 62 . 6: ) 400 ( = == =Defenisi dari electron Volt (eV)joules eV volt electron1910 602 . 1 ) ( 1 =Untuk menghindari pengunaan pangkat negatif yang besar (pada range 10-19) untuk energi foton (joule) maka didefinisikan satuan energi yang lebihmudah :1 electron volt = energi yag diproleh oleh sebuahfoton ketika ia dipercepat melalui sebuah bedapotensial 1 volt (J/C)Energi Foton dalam eVCahaya Biru (400 nm):E = 3.10 eVCahaya Hijau (587.6 nm): E = 2.11 eVCahaya Merah (700 nm): E = 1.77 eVphotoelectronTingkat Energi atom Ketika terjadiEfek FotolistrikElectron absorbs photon and jumps to higher energy levelTingkat-TingkatEnergi: PeristiwaPenyerapan FotonDengan menyerapfoton dengan energiyang cukup, sebuahelektron dapatmeloncat ke tingkatenergi yang lebihtinggi. Elektron memancarkan(emisi) foton danmeloncat ke tingkatenergi yang lebihrendah.Tingkat-TingkatEnergi: PeristiwaEmisi FotonTingkat-TingkatEnergi: PeristiwaEmisi FotonWhen an electron drops to a lower energy level, a photon is emittedAtomic Energy Levels Ground state (E0): lowest, most stable energy level in an atom: strongest electrostatic attraction between nucleus and electron lowest electron kinetic energy Excited states (E1 E2 etc.): with elevation to higher energy levels, electrons become less stable: weaker electrostatic attraction higher electron kinetic energy farther (on average) from nucleusPage 128Tingkat energi Level:Atom Hidrogenvolt electon eVstate excitation m wheremeVEm==+= ) ( 2 , 1 , 0) 1 (6 . 132Page 129Tingkat energi Level:Atom HidrogeneVeVE 6 . 1316 . 130 ==eVeVE 4 . 346 . 131 ==eVeVE 51 . 196 . 132 ==eVeVE 85 . 0166 . 133 ==) ( 2 , 1 , 0) 1 (6 . 132state excitation mmeVEm=+=Tanda Negatifindicates electrostatic attraction to nucleus (Binding Energy)Consider negative electron energy as the electrostatic hill that the electron must climb to be freed from the atomZero energy free electronAtomic Energy Diagram Shows all the valid energy levels for the atom. Energy required for an electron to jump to a higher level Photon energy released as an electron drops to a lower levelHydrogen Energy Diagram-14-13-7-9-8-10-11-12-20-1-3-4-5-6E0E1E2E3E4E50 eV10.2 eVTransition Level above Ground State (eV)Electron Energy (eV)13.6 eV12.74 eV12.09 eVIonization State91 nm121 nm486 nm656 nmHYDROGEN ENERGY LEVEL DIAGRAM103 nm97 nmFig 78, p 128Hydrogen Balmer series encompasses transitions up or down to/from the first excited state (E1).Note the hydrogen F line (E3 E1) and C line (E2 E1) Energy Levels: Hydrogen Atom After absorbing energy, the electron remains in an excited state for an extremely short period (~ 10 nsec) Spontaneous emission: as the unstable, excited electron drops to a lower energy level, it emits a photon. Photon energy is equal to the difference in atomic energy levelsEnergy Levels: Hydrogen AtomeV eV eV E E E 89 . 1 ) 4 . 3 ( 51 . 11 2= = = APhoton energy for the transition from E2to E1:nmeVnm eVEc h c hE 3 . 65689 . 1239 , 11== = =Hydrogen C-lineEnergy Levels: Hydrogen AtomnmeVnm eVEc h c hEeV eV eV E E E877 , 166 . 0239 , 166 . 0 ) 51 . 1 ( 85 . 012 3== = == = = A A single energy jump from a higher excited state causes a smaller energy transition (e.g. from E3to E2):Energy Levels: Hydrogen AtomeV eV eV E E E 55 . 2 ) 4 . 3 ( 85 . 01 3= = = A Multi-level energy transitions can also occur (e.g. from E3to E1): The greater the energy transition as an electron jumps to a lower energy level, the shorter the wavelength of the emitted photonnmeVnm eVEc h c hE 48655 . 2239 , 11== = =Hydrogen F-lineAtomic Spectra: HydrogenAll energy transitions (single-level and multi-level) are possible for the hydrogen atom.Photons corresponding to all possible transitions are emitted: gives rise to characteristic discrete spectral lines of low pressure H2gasAtomic Spectra: Hydrogen Discrete hydrogen spectral lines fingerprint for hydrogen. Discrete hydrogen spectra used extensively in astronomy Characteristic atomic spectra in a gas best seen at low pressure - at higher pressures, spectra begin to changeAtomic Spectra Bunsen burned salts containing various elements in a flame: placed a series of slits in front of the flame directed the light through a prism to disperse s This allowed him to view the line spectra of elementso ) 1 ( =glassn do1nSpectroscopeAbsorption vs. Emission SpectraAbsorption Spectrasamplesample400 nm500 nm600 nm700 nmwww.chem.uidaho.eduSolar Spectrumwww.chem.uidaho.eduAtomic SpectraThe colors of fireworks are created by atomic line spectraAtomic Spectra: Hydrogen Increasing gas temperature excites a greater proportion of H atoms more atoms spontaneously emitting photons Explains why gas discharge lamps glow brighter as they warm upAtomic Spectra Increasing gas pressure changes atomic spectra collisions between molecules also cause energy exchanges. As pressure increases, collision frequency increases discrete spectra gradually give way to acontinuous spectrumContinuous SpectrumQQ1. Which transition in the hydrogen atom would result in emission of the shortest wavelength photon?(A) E0 E1(B) E3 E1(C) E4 E1(D) E5 E2wrong direction3.4 0.85 = 2.55 eV3.4 0.54 = 2.86 eV1.51 0.38 = 1.13 eVQQ2. What type of atomic spectrum would most likely be seen for a hydrogen gas cloud in space?(A) Absorption spectrum(B) Emission spectrum(C) Continuous spectrum(D) All of the above Low pressure, cold gasPage 129Fraunhofer Lines (Solar Absorption SpectrumPage 129Designation Element Wavelength (nm) Designation Element Wavelength (nm)y O2 898.765 c Fe 495.761Z O2 822.696 F H 486.134A O2 759.370 d Fe 466.814B O2 686.719 e Fe 438.355C H 656.281 G' H 434.047a O2 627.661 G Fe 430.790D1 Na 589.594 G Ca 430.774D2 Na 588.997 h H 410.175D3 He 587.565 H Ca+396.847E2 Fe 527.039 K Ca+393.368b1 Mg 518.362 L Fe 382.044b2 Mg 517.270 N Fe 358.121b3 Fe 516.891 P Ti+336.112b4 Fe 516.751 T Fe 302.108b4 Mg 516.733 t Ni 299.444Major Fraunhofer Lines (Solar Spectrum)Solar Spectrum Series of absorption lines produced when sunlight emitted from the hotter solar chromosphere is absorbed by the cooler outer solar photosphere Hydrogen makes up 92.1% of the suns atoms, helium 9.2%, and sodium, calcium, and iron 0.1% Overall, several thousand solar Fraunhofer lines representing 67 elementsTable 1 Major Solar Fraunhofer LinesDesignation Wavelength (nm) OriginA 759.4 terrestrial oxygenB 686.7 terrestrial oxygenC 656.3 hydrogen (H)D1589.6 neutral sodium (Na I)D2589.0 neutral sodium (Na I)E 527.0 neutral iron (Fe I)F 486.1 hydrogen (H)H 396.8 ionized calcium (Ca II)K 393.4 ionized calcium (Ca II)FluorescencePage 129Fluorescence Fluorescence is an example of energy absorption followed by spontaneous photon emission. Many substances that can be raised by a stimulating source from ground state to an excited state, then spontaneously emit photons, will theoretically fluoresce.Page 129Fluorescence Typically a high frequency source (UV) is needed to raise atoms from the ground state. A fluorescent substance could undergo a single energy level transition: E0E1for excitation, followed byE1E0for spontaneous emission. This is rare. Most fluorescent substances, after excitation, will undergo a non-radiative transition (e.g. E2E1) followed by photon release (e.g. E1E0)Fluorescence (typical case)Fig 79, p 130Fluorescence Most substances are not 100% efficient, emitting less energy than they absorbed. Thermal agitation (vibrational loss) is the most common cause of the energy loss between absorption and emission (non-radiative transition) The emitted photon will therefore have lower energy than the exciting photonUV absorptionFlu