* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Physics 2DL Lectures
Survey
Document related concepts
Elementary particle wikipedia , lookup
Old quantum theory wikipedia , lookup
Atomic nucleus wikipedia , lookup
Bremsstrahlung wikipedia , lookup
Compact Muon Solenoid wikipedia , lookup
Quantum electrodynamics wikipedia , lookup
Future Circular Collider wikipedia , lookup
Monte Carlo methods for electron transport wikipedia , lookup
Introduction to gauge theory wikipedia , lookup
Theoretical and experimental justification for the Schrödinger equation wikipedia , lookup
Introduction to quantum mechanics wikipedia , lookup
Double-slit experiment wikipedia , lookup
Transcript
Physics 2DL Lectures Vivek Sharma Lecture # 2 Discussion of Experiments House Keeping Details Every one reported to the lab in assigned sections ? Know which experiment you are doing this week ? Could download pdf or WORD file of experiment ? We switched the web server hardware on you on last friday Helpful reading material on E-reserve Modern Physics: Serway, Moses, Moyer Modern Physics : Beiser Resnick-Halliday-Walker : Chapters on Interference & Diffraction But you could not tell (I hope) ! All should be accessible from UCSD computers of (UCSD web proxy) as PDF files Lectures: Plan Start with a brief overview of Physics behind the experiments Statistical analysis of data + advanced concepts in Probability Lecture Schedule In Light of My Travel 2D last quarter kept me tied to UCSD, Scientific responsibilities require me to travel to Europe in April & May Isola de Elba (Italy) Ringberg Castle, Bavaria I would like to schedule makeup lectures early in this quarter : Wednesday same time OK with you ? Additional Lecture this Week + Early Final Exam for 2DL ? Additional lecture to review experiments this WED same time ? Other dates : Wed 16 Apr, Fri 18 Apr, May 14th, May 16th There are 6 labs (1)+6 Weeks < 10 Weeks plenty of time Schedule Final exam (50 minutes, 3 problems) prior to the finals week to get this course out of your way? feedback please Tentative Date : 4th June ? Pl. keep checking the Class Announcements page at the 2DL web site: http://hepweb.ucsd.edu/~modphys/2dl03/an.html for late breaking information (rescheduled lectures, finals etc) Experiments You Will Do In No Particular Order 1. 2. 3. 4. 5. 6. 7. Optical Spectra & Diffraction Grating Coherence of Light & Interferometry Photoelectric Effect e/m of Electron Franck-Hertz Experiment Electron Diffraction Thermal Band Gap in Solids (optional because neither 2D or 4E will teach you this) Determination of e/m for Electron e/m is characteristic of a particle : electron Vs Cl- ion When Uniform magnetic field of strength B is established perpendicular to direction of motion of a charged particle, particle moves in a circular path of radius R mu 2 mu quB R R qB If electrons have KE = qV e 2V then 2 2 m B R e/m, e, m of Electron : Why Important Realization that electron is much less massive than the Hydrogen atom made physicists think about the structure Inside atom The electron was discovered just a bit over 100 years ago, triggered A scientific revolution Thomson’s idea Still used to measure Masses of fundamental Particles or nuclei The Photo Electric Effect: Nobel Prize for Einstein Maxwell’s Equations EM Wave Properties Hertz & Electromagnetic Waves ( Experiment) Description of Photoelectric Effect Einstein’s “Quantum” Interpretation inspired by Max Planck Bottomline : Failure of classical physics (why?) How EM waves propagate Interaction of EM waves with Matter How to prove that Einstein was right : Measure “h” Find it is same as in Blackbody radiation Maxwell’s Equations & EM Waves permeability permittivity EM Waves Energy Flow in EM Waves : 1 Poynting Vector S = ( E B) 0 Power incident on 1 S . A AE0 B0 Sin 2 (kx t ) an area A 0 Intensity of Radiation I = 1 2 0 c E02 Larger the amplitude of Oscillation More intense is the radiation Hertz : The EM Wave Guy Hertz : The EM Wave Guy PhotoElectric Effect Light of intensity I, wavelength and frequency incident on a photo-cathode Can tune I, f, Measure characteristics of current in the circuit as a fn of I, f, PhotoElectric Effect PhotoElectric Effect : E = h f = Quantized Franck-Hertz Experiment : A prelude Bohr Atom : Discrete orbit Emission & Absorption line classical Bohr’s quantization n2 2 rn , n 1 , 2,.... 2 mke n 1 Bohr Radius a0 ke2 Z 2 En 2 2a0 n Franck Hertz Experiment: Playing Football ! Inelastic scattering of electrons Confirms Bohr’s Energy quantization Electrons ejected from heated cathode At zero potential are drawn towards the positive grid G. Those passing thru Hole in grid can reach plate P and cause Current in circuit if they have sufficient Kinetic energy to overcome the retarding Potential between G and P Tube contains low pressure gas of stuff! If incoming electron does not have enough energy to transfer =E2-E1 then Elastic scattering, if electron has atleast KE= then inelastic scattering and the electron does not make it to the plate P Loss of current (J) Franck & (G) Hertz Experiment Current decreases because many Electrons lose energy due to inelastic Scattering with the Hg atom in tube And therefore can not overcome the Small retarding potential between GP The regular spacing of the peaks Indicates that ONLY a certain quantity Of energy can be lost to the Hg atoms =4.9 eV. This interpretation can be confirmed by Observation of radiation of photon energy E=hf=4.9 eV emitted by Hg atom when V0 > 4.9V