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Unformatted text preview: 1 1 Chapter 7 Atomic Structure 2 Light s Made up of electromagnetic radiation s Waves of electric and magnetic fields at right angles to each other. 3 Parts of a wave λ Wavelength Frequency = number of cycles in one second Measured in hertz 1 hertz = 1 cycle/second 4 Frequency = ν 5 Kinds of EM waves s There are many s different λ and ν s Radio waves, microwaves, x rays and gamma rays are all examples s Light is only the part our eyes can detect Gamma Rays Radio waves 6 The speed of light s in a vacuum is 2.998 x 10 8 m/s s = c s c = λν λν λν λν s What is the wavelength of light with a frequency 5.89 x 10 5 Hz? s What is the frequency of blue light with a wavelength of 484 nm? 2 7 In 1900 s Matter and energy were seen as different from each other in fundamental ways s Matter was particles s Energy could come in waves, with any frequency. s Max Planck found that the cooling of hot objects couldn’t be explained by viewing energy as a wave. 8 Energy is Quantized s Planck found ∆ E came in chunks with size h ν s ∆ E = nh ν s where n is an integer. s and h is Planck’s constant s h = 6.626 x 1034 J s s these packets of h ν are called quantum 9 Einstein is next s Said electromagnetic radiation is quantized in particles called photons s Each photon has energy = h ν = hc/ λ s Combine this with E = mc 2 s you get the apparent mass of a photon s m = h / ( λ c) 10 Which is it? s Is energy a wave like light, or a particle? s Yes s Concept is called the Wave Particle duality. s What about the other way, is matter a wave? s Yes 11 Matter as a wave s Using the velocity v instead of the frequency ν we get s De Broglie’s equation λ = h/mv s can calculate the wavelength of an object 12 Examples s The laser light of a CD is 7.80 x 10 2 m. What is the frequency of this light? s What is the energy of a photon of this light? s What is the apparent mass of a photon of this light? s What is the energy of a mole of these photons? 3 13 What is the wavelength? s of an electron with a mass of 9.11 x 1031 kg traveling at 1.0 x 10 7 m/s? s Of a softball with a mass of 0.10 kg moving at 125 mi/hr? 14 How do they know? s When light passes through, or reflects off, a series of thinly spaced lines, it creates a rainbow effect s because the waves interfere with each other. 15 A wave moves toward a slit. 16 Comes out as a curve 17 with two holes 18 with two holes Two Curves 4 19 Two Curves with two holes Interfere with each other 20 Two Curves with two holes Interfere with each other crests add up 21 Several waves 22 Several waves Several Curves 23 Several waves Several waves Interference Pattern Several Curves 24 What will an electron do? s It has mass, so it is matter....
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This note was uploaded on 09/28/2009 for the course CHEM 102 taught by Professor Freeman during the Spring '08 term at South Carolina.
 Spring '08
 FREEMAN
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