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Sp00 Midterm solutions

# Introductory Nuclear Physics

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PHY431 Midterm Spring 2000 1 5/2/2000 Short-Answer Questions 1. Define alpha, beta, and gamma radiation. For each type, write down an example of a reaction in which such radiation is emitted. alpha radiation : emission of strongly bound 2p-2n cluster (He nucleus): 238 U 234Th + α beta radiation : emission (or capture) of electron plus neutrino, or emission of positron plus neu- trino: 64 Cu 64 Ni + e + e + + ν e is β radiation. gamma radiation : emission of high-energy photons from nuclear de-excitation 2. In what experimental features does scattering of alpha particles as observed by Rutherford differ significantly from predictions from the Thomson “plum-pudding” model of the atom? occasional large-angle scatters, which could not occur in a Thomson model. 3. For Rutherford scattering off an Aluminum ( A =27, Z =13) foil, calculate the alpha particle energy for which deviations from the Rutherford scattering formula ought to occur. for K > ( e 2 /4 πε 0 )( zZ/R ) = (1/137)(2 × 13/(1.2 × 27 1/3 fm)) = 10.4 MeV (ignoring the size of the α ) 4. List all the known leptons, their spins, and their electric charges. All are spin-½ fermions; the charged leptons: e , µ , τ and the uncharged neutrinos: ν e , ν µ , ν τ . 5. List all the known quarks, their spins, and their electric charges. All are spin-½ fermions; the charge + 2 / 3 quarks: u , c , t, and the charge 1 / 3 quarks: d , s , b . 6. List the interactions that quarks and leptons have (an- swer Y or N, or specify): 7. List the carriers, with spin and charge , of the (i) Electromagnetic force: photon: γ , charge 0, spin 1 (ii) Weak interaction: W ± , Z 0 , spin 1 (iii) Strong interaction: 8 gluons, charge 0, spin 1 8. Describe two experimental methods used to study the nu- clear charge distribution. i) electron scattering off nuclei ii) muonic atoms 9. Sketch the expected nuclear charge density as function of radius for a spherically symmetric A =58 nucleus. Label the axes with the proper nuclear density (MeV/fm 3

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Sp00 Midterm solutions - PHY431 Midterm Spring 2000 1...

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