INTRO MODERN PHYSICS
INTRO MODERN PHYSICS PHY 3101
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This 4 page Class Notes was uploaded by Mrs. Linda Wiegand on Friday September 18, 2015. The Class Notes belongs to PHY 3101 at University of Florida taught by Staff in Fall. Since its upload, it has received 11 views. For similar materials see /class/206779/phy-3101-university-of-florida in Physics 2 at University of Florida.
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Date Created: 09/18/15
Errata Modern Physics Tipler and Llewellyn Third Edition 0 p 189 Summary Should be Z 2 in formula for Bohr energies 2on n 2 n o p 582 Formula 12 14 Reaction should be of deuterium plus tritium not two tritium nuclei 2 H H 0 Appendix A Le out 8Be with an atomic mass of 8005304 You need it for problem 1130 0 Problem 1 39 Correct equation should be GAUZ A 2 GAI39Y My 0 Problem 1 44 Error in length contraction formula Exponent should be 12 not 12 0 Problem 2 47 Missing a proton in the reaction Should be ppgtppppbar 0 Problem 3 26 ux of photons not quotprotonsquot 0 Problem 11 30 Need mass of 8Be which is not in Appendix A Astrophysical Constants o l lightyear o l parsec o Radius of Ea1th 0 Mass of Ea1th o Radius of Sun 0 Mass of Sun 0 Earth Sun separation 0946 gtlt1016 m 32621y 3086 x1016 m R6 6378 gtlt106 m M6 59722 gtlt1024 kg R0 6961gtlt108 m MO 19884gtlt1030 kg 1 AU 1496 gtlt1011 m o Gravitational Constant G 667390 x 10 11 m3 kg s2 Darin Acosta Page 1 122001 PHY3101 Modern Physics Lecture Notes Spin 1 Angular Momentum and Spin Disclaimer These lecture notes are not meant to replace the course textbook The content may be incomplete Some topics may be unclear These notes are only meant to be a study aid and a supplement to your own notes Please report any inaccuracies to the professor Magnetic Dipoles Consider a small current loop For distances R gt gt r the loop radius the calculation of the magnetic eld does not depend on the shape of the current loop It only depends on the current and area as well as R and 9 Br21A cos39 f R sin9 39114 3 R Here I is the current in the loop A is the loop area R is the radial distance from the center of the loop and 9 is the polar angle from the Z axis The eld is equivalent to that from a tiny bar magnet a magnetic dipole De ne the magnetic dipole moment to be a vector pointing out of the plane of the loop lt5 D Acosta Page 1 132001 PHY3101 Modern Physics Lecture Notes Spin 1 When placed in an extemal magnetic eld a magnetic dipole feels a torque A B f I X B ll This cause the dipole to precess around B The potential energy of a magnetic dipole in an extemal magnetic eld is V 1 3 The lowest energy con guration is for It and 3 parallel Work energy is required to reallgn the magnetic dipole in a B eld B N B l l E H Lowest energy Highest energy Atomic Dipoles An electron orbiting an atom is like a small current loop Let s consider rst a classical model of the atom with the electron in a circular orbit We can determine the magnetic dipole moment as follows T E period v 6 WT r2 erv 2727 r 2 3 lJ But angular momentum is de ned as L I7 X f7 L l El rp mvr for circular orbits This implies D Acosta Page 2 132001
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