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123Cex3verCsol - Name_Student ID Score last first I Matter...

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Name ___________________________________ Student ID ____________ Score _______ last first Physics 123C, Spring 09, Version C Exam 3, page 1 I. Matter Waves A beam of neutrons (rest mass 1 . 675 × 10 -27 kg) of kinetic energy 9 . 00 × 10 -16 J strikes a diffraction grating. Assume that the grating slits are very small (sub- atomic-sized) dimension in the horizontal width, but macroscopic (about 2 mm) in the vertical dimension. 1. (5 pts) Which choice best represents the deBroglie wavelength of these neutrons? 2 . 21 × 10 -10 m 1 . 32 × 10 -13 m 1 . 87 × 10 -13 m 3 . 82 × 10 -13 m 2 . 62 × 10 12 m A B C D E 2. (5 pts) Which choice best represents a physics law or principle that could be used to explain why a neutron does not follow a straight path through the grating to the screen? A. Conservation of Energy. B. Heisenberg Uncertainty Principle. C. Stefan-Boltzmann Radiation Law. D. Planck’s Quantization Principle. E. Conservation of Angular Momentum. Useful Data: h = 6 . 63 × 10 -34 J s 1 . 000 eV = 1 . 602 × 10 -19 J ' Incoming neutrons Diffraction grating Screen Pattern on screen White = many neutrons
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