68110943-Midterm-1-Solved-Problems - Solved Problems 1(a...

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Solved Problems 1. (a) What is the size of an atom? (b) What is the velocity of an electron in the first Bohr orbit of an Hydrogen atom? Solution a) You can estimate size of an atom as Or you can calculate Bohr radius that gives size of an atom: quantization of angular momentum Force between proton and electron. Eliminating velocity between equations we obtain: For n=1; substituting: b) Quantization of angular momentum yields: Compare to the speed of light: 2. Calculate frequency and energy of the photons, in eV, having a wavelength: a) Radio wave 900 meter b) Microwave 3.0 cm c) Visible light range 500 nm d) x-ray range 5.0 nm e) Gamma ray 1.0 pm Solution Energy of the photon is given by ; c=3 a) OR Think!! Which of the wave is more energetic? What is the energy of FM radio signals? Why are Gamma rays dangerous?? You can solve the remaining part of the problem. 3. Radiation has been detected from space that is characteristic of an ideal radiator at (Relic from “Big-Bang”). For this temperature at what wavelength does
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the Planck distribution peak? In what part of the electromagnetic spectrum is this wavelength? Solution
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This note was uploaded on 01/12/2012 for the course CHEM 133 taught by Professor Staff during the Spring '08 term at UCSD.

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68110943-Midterm-1-Solved-Problems - Solved Problems 1(a...

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