Lect24_[Compatibility_Mode]

Lect24_[Compatibility_Mode] - Physics 344 Foundations of...

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Physics 344 Foundations of 21 st Century Physics: Relativity, Quantum Mechanics and heir Applications Their Applications Instructor: Dr. Mark Haugan Office: PHYS 282 [email protected] TA: Dan Hartzler Office: PHYS 7 [email protected] Grader: Shuo Liu Office: PHYS 283 [email protected] Office Hours: If you have questions, just email us to make an ppointment. e enjoy talking about physics! appointment. We enjoy talking about physics! Notice: There is a typo in problem 4 part d) on this week’s homework. The reaction equation for that part should read pn + vpn μ +→
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Question 1: Why is this electromagnetic decay of the Λ 0 particle never observed? ) because 4 omentum cannot be conserved 0 n γ Λ →+ A) because 4-momentum cannot be conserved B) because strangeness is not conserved C) because meson number is not conserved D) because baryon number is not conserved Answer: The presence of the photon in the final state identifies this as an electromagnetic decay process, but because the electromagnetic interaction conserves strangeness this decay is not allowed. In the Standard Model, strangeness is a measure of net strange quark number. Electromagnetic and Strong interactions can only create or destroy strange quarks paired with their antiparticles.
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Light: Waves and Particles When we discussed Compton scattering recently we found it simplest to exploit 4-momentum conservation by using the photon model of the electromagnetic radiation scattering from an electron. On the other hand, you learned last semester that such radiation consists of electromagnetic wave fields that satisfy Maxwell’s equations, that are generated by accelerated charges and that exert forces on charges as described by the orentz force law on q by field Fq E q v B = G GG G Lorentz force law incident wave The wave model explains scattering s a process in which scattered (re-radiated) wave as a process in which an incident wave accelerates a charge. his causes the charge cident wave This causes the charge to emit the scattered radiation we observe and explains the change the charge’s energy and incident wave plus re-radiated wave momentum that we observe. In the coming days we will be blending these two models of light into a single quantum theory.
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We begin this work by using the wave model of light to discuss the transport of energy and momentum by electromagnetic radiation. Eventually, we will be able to tie this to the corresponding account of energy and momentum carried by photons in a way that allows us to predict the probability of detecting hotons at different places and times. photons at different places and times.
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This note was uploaded on 11/26/2010 for the course PHYS 344 taught by Professor Garfinkel during the Spring '08 term at Purdue.

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Lect24_[Compatibility_Mode] - Physics 344 Foundations of...

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