Chem Test

Chem Test - 1 Self Evaluation#1 V 2(Chem20A-1 F'06...

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1 Self Evaluation #1 V. 2 (Chem20A-1 F’06, 10/24/06 6:00-8:00pm, 100+5pts, max=100pts) Name :___________ Section: ___ Signature :_________ ___ ______ Signature (please sign again) :____________________ By writing down my name, I confirm that I strictly obey the academic ethic code when taking this exam. (i) In order to have your SE#1 graded, your signature above must match the ones in our record. (ii) Four questions. Please budget your time. You may want to start with the parts you are more familiar with. Relax and you will perform better. (iii) One extra-credit question, but the total score is capped by 100 points. (iv) Formula sheets are attached at the end. Need more formula? Just raise your hand. (v) It’s important to show calculation or algebraic details. (vi) Coverage: shown below. (vii) Academic ethics need to be strictly obeyed. No exceptions and no kidding. Theme of Self Evaluation #1:. Downfall of classical mechanic and the salvation provided by quantum chemistry [1] The Downfall of Classical Mechanics: Particle-Wave Dual Properties (total=28 pts) In the early 1900s, a number of key experiments showed that the prediction of classical mechanics were inconsistent with experimental outcomes. The following are a few examples. (a) Energy of photons (5 pts) Through studying the mystery of “blackbody radiation” (not covered in this course), Planck proposed in 1903 that the energy of a photon can be expressed as E photon =h ν. Please solve the following question.
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2 (b) Photoelectric effect (5 pts) Classical mechanics fails to model the particle property of waves. In 1905, Einstein proposed the following equation to explain the mystery of the photoelectric effect and got the 1921 Nobel prize in Physics. Based on “conservation of total energy”, please derive this equation. Please clearly explain your arguments within the space provided. (Hint: the photo below) (c) Photoelectric effect: numerical calculation (6 pts)
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3 (d) de Broglie matter wave (6 pts) Classical mechanics fails to describe the wave property of matters. By assuming (i) the angular momentum is quantized: L = mvr = n ħ , and (ii) the quantum wave of a orbiting particle forms a circular standing wave, please derive the de Broglie relation : λ =h/(mv)=h/p. Please show algebraic details. (e) Uncertainty Principle (6 pts) Classical mechanics suggests that we can measure simultaneously and with certainty all the properties of a system such as position, linear momentum, energy, etc. This violates experimental observation made on microscopic objects such as electrons, atoms, etc. This flaw was fixed in 1927 by Heisenberg’s Uncertainty Principle: x p ħ /2. Please solve the following question.
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This note was uploaded on 04/08/2008 for the course CHEM 20A taught by Professor Scerri during the Fall '05 term at UCLA.

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Chem Test - 1 Self Evaluation#1 V 2(Chem20A-1 F'06...

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