Corso di Fisica Moderna

Corso di Fisica Moderna a.a. 2011/12 2nd semestre Indeterminazione: Variabili coniugate 1)  X e P sono variabili dinamiche misurabili in ogni istante 2)  Il tempo è una variabile indipendente, quindi non è una grandezza osservabile in senso streDo •  anche se una parFcella non può avere simultaneamente posizione e impulso ben definiF, l'energia si può misurare con precisione arbitraria in ogni istante di tempo. ΔE è la differenza tra due valori esaM dell'energia misuraF in due istanF diversi. Se la durata di uno stato (ad es. la vita media di una parFcella) è limitata, la sua energia è indefinita Quantum Physics grew out of Launched by experiments such as Failures of Classical Physics Which found some quantum remedies in the and Planck Hypothesis Wave-­‐parFcle duality And generated new ideas like the Uncertainty Principle and Quantum StaFsFcs Describes nature with StarFng with WavefuncFon Photoelectric effect and Blackbody radiaFon Used in Bohr Theory Led to Quantum numbers Compton ScaDering Which led to Hydrogen Energies Leading to RadiaFon curves Wien Displacement Law Schrodinger EquaFon Hydrogen Spectrum Atomic ProperFes Periodic Table And started analysis of Atomic Structure Quantum experiments ParFcle nature of light Photoelectric Effect Wave nature of electron Cavity radiaFon Davisson-­‐
Germer Experiment Blackbody radiaFon Compton ScaDering Nuclear atom Rutherford ScaDering ParFcle nature of light Discrete Atomic Spectral Lines QuanFzed atomic energy levels Franck-­‐Hertz Experiment Electron spin Stern-­‐Gerlach experiment What is an atom? 1) 
2) 
3) 
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Size Mass and its measure Mass spectrometers Atomic models Atomic Size Deflected out of the beam Density n infinitesimal Lambert-­‐Beers law Debye-­‐Scherrer method: MonochromaFc radiaFon diffracted by a polycrystalline sample. 2d sin ! = n"
Electron density distribuFon Different probes: 1)  Electrons (9 10-­‐17 m (cl. 2.8 10-­‐15 m)) 2)  Light 3)  Neutrons (1.11 10-­‐15 m ) 4)  alpha parFcles (nuclei) Lenard’s experiment: Electronic probe Transmission electron microscope Title : The Beginning Media : Xenon on Nickel (110) Atomic masses Mass Spectroscopy Atomic Models Nucleus: Thomson’s model Nucleus: Thomson’s model Rutherford’s experiment Rutherford, Geiger, Marsden experiments. Using the repulsive Coulomb force we obtain an hyperbolic soluFon of the trajectory of the alpha parFcle. It’s equal to the distance of the closest approach to the nucleus in a head-­‐on collision b=0 ! 1 zZe 2 1
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The scaDering angle θ follows by finding the value of φ as r tends to ∞ and seMng θ=π-­‐φ The probability that a parFcle will pass through one of these rings Cross-­‐SecFon of the Rutherford scaDering The Rutherford scaDering formula is usually expressed in terms of a differenFal cross secFon dN =
d!
Ind!
d!
The number dN of alpha-­‐parFcles scaDered into a solid angle dΩ