Physics 107: Ideas of Modern Physics Exam 4 May 11, 2007 Name______________________________________________________ ID #_________________________ Section #______________ On the Scantron sheet, 1) Fill in your name 2) Fill in your student ID # (not your social security #) 3) Fill in your section # (under ABC of special codes) Fundamental constants: c= speed of light = 3x108 m/s g= accel. of gravity on Earth = 10 m/s2 G= gravitational constant = 6.7x10-11 N-m2/kg2 1 eV = 1.6 x 10-19 Joules Photon energy E = hc/λ = 1240 eV-nm/λ2 2 1. B 2 Which of the following is true of fusion a. Fusion is induced by neutron absorption b. Fusion reactors provide part of the energy consumed in this country. c. Only light elements are used as fuel in fusion reactors d. The daughter products of fusion are lighter than the initial nuclei. e. The idea of fusion was developed only ten years ago. 3. About 1 MeV (106 eV) of energy per nucleon is released during the fission of 235U. About how many 235U nuclei per second (there are many nucleons in a nucleus) fission in a reactor that produces 50 mega-watts (50x106 Watts) of power? a. 1.3x1018 nuclei/sec b. 50 x 106 nuclei/sec c. 1.2 x 1012 nuclei/sec d. 0.2 nuclei/sec e. 170 nuclei/sec 4. In order for a particle to couple to the gluon field, it must have a. flavor b. mass c. color charge d. electric charge e. all of the above 5. An electron and a positron are at rest, and each separately have a mass of 0.5 MeV/c2 (1 MeV = 106 eV). They annihilate to produce two photons. Each photon has a wavelength of a. 0.005 nm b. 0.0025 nm c. 0.5 nm d. 2.5x103 nm e. 2.5 nm3 3 6. Which of these fundamental particles is not a matter particle a. gluon b. electron c. tau d. muon e. all of them are 7. A proton is a composite particle consisting of three up and down quarks, (up charge = +2/3e, and down charge = -1/3e). Which is the quark structure of the proton? a. up, up, down b. up, up, up c. down, down, down d. up, down, down e. none of these 8. The force that binds together quarks into hadrons is a. Gravitational force b. Electromagnetic force c. Strong force d. Weak force e. none of these 9. In the Ice Cube neutrino telescope, neutrinos can be detected because they change into muons in the Antarctic ice. The interaction responsible for this is a. the weak interaction b. the strong interaction c. the gravitational interaction d. the electromagnetic interaction e. none of these 10.Which of these particles represents an excited state of the weak interaction field? a. tau b. neutrino c. photon d. top quark e. W+4 4 11. Which of these particles does not mediate a fundamental force? a. photon b. gluon c. muon d. W e. all of them do 12. In quantum field theory, two particles interact only when a. both particles have electric charge b. a mediating field is excited c. the probabilities are uncertain d. one of the particles is moving e. one of the particles is a muon 13. Which of the following interactions can change one fundamental particle into another? a. Weak interaction b. Strong interaction c. Electromagnetic interaction d. Gravitational interaction e. none of these 14. How many generations of leptons and quarks are in the standard model? a. 1 b. 2 c. 3 d. 4 e. 5 15. The difference between the different generations of leptons is a. their color b. their charge c. their shape d. their spin e. their mass5 5 16. Which of these particles do not interact via the electromagnetic force? a. neutrino b. electron c. quark d. tau e. they all do 17. Matter is made of a. quarks only b. leptons only c. quarks and leptons only d. gluons only e. quarks and gluons only 18. The standard model is modified by adding an extra field called the Higgs field, whose excitation is the Higgs boson. Coupling of fundamental particles to this field gives the particles a. mass b. charge c. color d. spin e. flavor 19. Strings interact a. by exchanging field particles b. via the strong interaction c. by changing color d. by joining and splitting e. by exchanging spin 20. In string theory, different fundamental particles appear as a. different quantum interactions between strings b. quantum strings of different color c. quantum strings of different length d. different quantum vibrations of strings. e. quantum strings of different velocity 21. Particle physics is important in understanding the big bang because a. the big bang was very loud b. time passed quickly at big bang c. energies were extremely high at big bang d. black holes dominated the big bang e. long time has passed since big bang
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