Chem 1211 1st Edition Lecture 16Outline of Last Lecture I. Thermochemical Equations ContinuedOutline of Current Lecture I. WavesII. Electromagnetic RadiationIII. Photoelectric EffectCurrent LectureI. Wavesa. Conceptest: Which colors are arranged from lowest to highest frequencies?i. Blue, green, redii. Yellow, blue, greeniii. Green, yellow, rediv. Red, yellow, blue 1. Answer: red, yellow, blue2. 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 BIVb. 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 metersii. Reasoning: c=wf, so 3x108 = (2.45x109)w. Your answer, .122, is in metersII. Electromagnetic Radiationa. E=hfi. H is a constant named after Max Planck (Planck’s constant)1. 6.626 x 10-34 Jsb. ConcepTest: What is the energy of .122 m radiation from a microwave oven?i. Answer: 1.63 x 10-24 JThese 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.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 wayd. Cosmic rays, x-rays, and UV= ionizing radiation (1 photon can make molecules fallapart)III. Photoelectric Effecta. ConcepTest: Which statements are TRUE concerning the photoelectric effect?i. Discovered by Albert Einstein, who received a Nobel Prize for this discoveryii. Electrons ejected from a metal surfaceiii. Require an energy threshold1. ANSWER: i and iii 2. Reasoning: electrons are ejected from the metal surface, not protonsb. 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 effectd. ConcepTest: Which statements are TRUE concerning the emission spectra? i. Series of discreet linesii. Predicted by the Bohr atomic modeliii. Characteristic of specific elements1. ANSWER: i, ii, and
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