Chem 1211 1st Edition Lecture 16 Outline of Last Lecture I Thermochemical Equations Continued Outline of Current Lecture I Waves II Electromagnetic Radiation III Photoelectric Effect Current Lecture I II Waves a Conceptest Which colors are arranged from lowest to highest frequencies i Blue green red ii Yellow blue green iii Green yellow red iv Red yellow blue 1 Answer red yellow blue 2 Reasoning Wavelength and frequency are inverses as wavelength goes down frequency goes up Red has the greatest wavelength so it has the lowest frequency Follow ROY G BIV b C speed of light 3 x 108 mps w wavelength in meters x f frequency in Hertz c ConcepTest Microwave ovens operate at 2 45x109 Hz What is the wavelength of that radiation i Answer 122 meters ii Reasoning c wf so 3x108 2 45x109 w Your answer 122 is in meters Electromagnetic Radiation a E hf i H is a constant named after Max Planck Planck s constant 1 6 626 x 10 34 Js b ConcepTest What is the energy of 122 m radiation from a microwave oven i Answer 1 63 x 10 24 J These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute III ii Reasoning To find the energy use the equation e hf but first you need to find the frequency You know the wavelength 122m so plug it into the equation c wf to get a frequency of 2 45x109 Hz Then multiply that frequency times Planck s constant to get the energy c Cosmic rays x rays UV visible infrared microwave radiowave energy and frequency wavelength increase this way increases this way d Cosmic rays x rays and UV ionizing radiation 1 photon can make molecules fall apart Photoelectric Effect a ConcepTest Which statements are TRUE concerning the photoelectric effect i Discovered by Albert Einstein who received a Nobel Prize for this discovery ii Electrons ejected from a metal surface iii Require an energy threshold 1 ANSWER i and iii 2 Reasoning electrons are ejected from the metal surface not protons b Light strikes the surface of some metals causing electrons to be ejected if the E of the electron is of sufficient magnitude c Albert Einstein explained this effect d ConcepTest Which statements are TRUE concerning the emission spectra i Series of discreet lines ii Predicted by the Bohr atomic model iii Characteristic of specific elements 1 ANSWER i ii and iii
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