Svjetlost, svuda, svjetlost oko nas (pardon, elektromagnetsko zračenje) Uvod u spektroskopiju Predavanje 2

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1 Svjetlost, svuda, svjetlost oko nas (pardon, elektromagnetsko zračenje) Uvod u spektroskopiju Predavanje 2

2 Osnove optike Što je to svjetost? I. I. Newton (1704 g.) "Opticks Čestice (korpuskule) Svjetlost se sastoji od čestica. Prizma (1666 g.) Reflektirajuci teleskop (1668 g.) Teorija boje Duga Newtonov genije; objašnjenje niza fenomena II. Christian Huygens Traité de la Lumière valna (undularna) teorija svjetlosti, no bez exp.

3 Svjetlost Kraj XVIII. stoljeća i početak XIX. stoljeća Novi eksperimenti (Young, Fresnel, Arago, Helmholtz, Fraunhofer,...) difrakcija (ogib) Y interferencija Y polarizacija F svjetlost je VAL transverzalni! F (Y mala t komp, velika l komp; F samo t komp)

4 Svjetlost Kraj XVIII. stoljeća i početak XIX. stoljeća Novi eksperimenti (Young, Fresnel, Arago, Helmholtz, Fraunhofer,...) difrakcija (ogib) Y interferencija Y polarizacija F svjetlost je VAL transverzalni! F (Y mala t komp, velika l komp; F samo t komp) Robinson, Andrew (2007). The Last Man Who Knew Everything: Thomas Young, the Anonymous Genius who Proved Newton Wrong and Deciphered the Rosetta Stone, among Other Surprising Feats. Penguin. isti Young: - Youngov modul elasticnosti - Young + Champollion = prijevod kamena iz Rosete - osnivac fizioloske optike: prilagodba oka na udaljenost objekta, astigmatizam - teorija kapilarnosti - hemodinamika; rule of thumb za doziranje lijekova kod djece - Languages : usporedba 400 jezika; pojam Indo-europski jezici - Young temperament : metoda za tuniranje instr.

5 Sir Isaac Newton (E) (4 January March 1727) François Arago (F) (26 Feb Oct. 1853) Thomas Young (E) (13 June May 1829) Hermann von Helmholtz (G) (31 August Sept. 1894) Augustin-Jean Fresnel (F) (10 May July 1827) Joseph von Fraunhofer (G) (6 March June 1826)

6 Longitudinalni valovi Gibanje čestica U SMJERU širenja vala (zvuk, kuglice na koncu, valovi u cvrstom tijelu) Transverzalni valovi Gibanje čestica OKOMITO na smjer širenja vala (valovi na vodi, valovi u cvrstom tijelu, spaga ) Elektromagnetski valovi???

7 Table 1: Seismic Waves Wave Type (and names) Particle Motion Typical Velocity Other Characteristics P, Compressional, Primary, Longitudinal Alternating compressions ( pushes ) and dilations ( pulls ) which are directed in the same direction as the wave is propagating (along the ray path); and therefore, perpendicular to the wavefront. V P ~ 5 7 km/s in typical Earth s crust; >~ 8 km/s in Earth s mantle and core; ~1.5 km/s in water; ~0.3 km/s in air. P motion travels fastest in materials, so the P- wave is the first-arriving energy on a seismogram. Generally smaller and higher frequency than the S and Surface-waves. P waves in a liquid or gas are pressure waves, including sound waves. S, Shear, Secondary, Transverse Alternating transverse motions (perpendicular to the direction of propagation, and the ray path); commonly approximately polarized such that particle motion is in vertical or horizontal planes. V S ~ 3 4 km/s in typical Earth s crust; >~ 4.5 km/s in Earth s mantle; ~ km/s in (solid) inner core. S-waves do not travel through fluids, so do not exist in Earth s outer core (inferred to be primarily liquid iron) or in air or water or molten rock (magma). S waves travel slower than P waves in a solid and, therefore, arrive after the P wave. L, Love, Surface waves, Long waves Transverse horizontal motion, perpendicular to the direction of propagation and generally parallel to the Earth s surface. V L ~ km/s in the Earth depending on frequency of the propagating wave, and therefore the depth of penetration of the waves. In general, the Love waves travel slightly faster than the Rayleigh waves. Love waves exist because of the Earth s surface. They are largest at the surface and decrease in amplitude with depth. Love waves are dispersive, that is, the wave velocity is dependent on frequency, generally with low frequencies propagating at higher velocity. Depth of penetration of the Love waves is also dependent on frequency, with lower frequencies penetrating to greater depth. R, Rayleigh, Surface waves, Long waves, Ground roll Motion is both in the direction of propagation and perpendicular (in a vertical plane), and phased so that the motion is generally elliptical either prograde or retrograde. V R ~ km/s in the Earth depending on frequency of the propagating wave, and therefore the depth of penetration of the waves. Rayleigh waves are also dispersive and the amplitudes generally decrease with depth in the Earth. Appearance and particle motion are similar to water waves. Depth of penetration of the Rayleigh waves is also dependent on frequency, with lower frequencies penetrating to greater depth.

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12 Partial cross section of the Earth showing major layer boundaries, approximate P-wave seismic velocities (Vp), and approximate ray path for P- and S-waves from a shallow earthquake to a seismograph at about 18 degrees (~2000 km) distance. (

13 Elektromagnetski valovi Transverzalni valovi gibanje čestica (medija) OKOMITO na smjer širenja vala Čestice, medij??? (kraj XIX. stoljeća) Eter medij u kojem se sire el. mag. valovi Niz eksperimenata (M&M 1887.) & Einstein: nema etera Maxwellove jednadžbe teorijska pretpostavka (1864.) Herzov (umro s 36 g.) eksperiment eksperimentalna potvrda (1887.) It's of no use whatsoever[...] this is just an experiment that proves Maestro Maxwell was right - we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there.

14 ELEKTROMAGNETSKI valovi imaju valna svojstva (ogib, interferencija) Cesticna svojstva, komad energije c foton Dualna priroda svjetlosti (I. Supek, M. Furic, Pocela fizike, Skolska knjiga, Zagreb (1994)) h Pitanje: Koja dva eksperimenta pokazuju valno-cesticnu prirodu svjetlosti?

15 Dualna priroda svjetlosti Moze li se fotoelektricni efekt objasniti valnom prirodom svjetlosti? Zasto? alnature.xml s.php?sim=photoelectric_effect

16 Spektroskopija (Fraunhofer) Bavi se elektromagnetskim zračenjem.

17 Što je spektar? Ovisnost intenziteta svjetlosti iz nekog izvora o valnoj duljini. Spektar Sunca Zasto se onda Sunce cini zutim?

18 Što je spektar? Ovisnost intenziteta svjetlosti iz nekog izvora o valnoj duljini. Spektar Sunca

19 Spektroskopija: atomska i molekularna Vrste spektara: kontinuirani nema spektralnih linija apsorpcijski tamne linije na kontinuiranom spektru emisijski izolirane linije

20 Spektroskopija: atomska i molekularna Vrste spektara: kontinuirani nema spektralnih linija apsorpcijski tamne linije na kontinuiranom spektru emisijski izolirane linije

21 Izvori svjetlosti Diskretni prijelazi Linijski spektri atoma Fraunhofer, (L. Ponomarev Kvantna kocka, Moderna fizika, Zagreb)

22 Izvori svjetla Zračenje crnog tijela Emitirano zračenje kao funkcija valne duljine

23 Izvori svjetla Zračenje crnog tijela Gorenje (temperatura) Lime light (zagrijani vapnenac) Žarulja (žari) ovisno temperaturi dobivamo zračenje (1802.) ako radi na višoj temperaturi imamo bijelo svjetlo Halogene žarulje (inertni plin + I ili Br) pomak prema plavom (1882.) Emitirano zračenje ovisi o TEMPERATURI. Mi bi željeli Sunce; 6000 K

24 Izvori svjetla Zračenje crnog tijela Gorenje (temperatura) Lime light (zagrijani vapnenac) Žarulja (žari) ovisno temperaturi dobivamo zračenje (1802.) ako radi na višoj temperaturi imamo bijelo svjetlo Halogene žarulje (inertni plin + I ili Br) pomak prema plavom (1882.) Emitirano zračenje ovisi o TEMPERATURI. Mi bi željeli Sunce; 6000 K

25 I mi zračimo!!!!

26 Spektar Sunca spektar crnog tijela Ima li bolje crno tijelo od Sunca? Planckian locus

27 Spektar Sunca spektar crnog tijela r/1999/99_pmb_2.pdf Ima li bolje crno tijelo od Sunca? grafit Ni-P slitine (e = 0.97) zid karbonskih nanocjevcica (e = 0.99)

28 Zakoni zracenja crnog tijela Rayleigh-Jeansov zakon B ( T) 2ckT 4 Planckov zakon 2 2c h B ( T) 5 hc kt e 1 Wienov zakon (pomaka) m T b Stefan-Boltzmannov zakon * 4 j T 5 2 k 2 15c h 4 3 "On the Law of Distribution of Energy in the Normal Spectrum". Annalen der Physik 4 (1901)

29 Spektar i boja nejednoznačnost istu boju možemo dobiti raznim spektralnim raspodjelama! metamerizam (spektrofotometar rjesava stvar) u/research/exploratory/free Software/repository/edu/br own/cs/exploratories/apple ts/spectrum/metamers_gui de.html u/courses/cs178/applets/c olormatching.html