Chapter 6

# Chapter 6 - 1 2 3 What is light Light is a combination of...

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1 1 2 3 What is light Light is a combination of an electric & magnetic field, oscillating very rapidly as it is propagating through space. Light has the properties of a wave. Electric vector Magnetic vector Direction of Propagation Source λ = wavelength A m p li t u d e

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2 4 Wavelength and Frequency Section 6.1 5 Summary of Frequency Wavelength Relationship 6 Continuous Spectrum Section 6.1
3 7 Mathematical Relationships ν = c λ speed of light, 3.0 x 10 8 m/s frequency, seconds -1 wavelength, m Section 6.1 8 Practice Problem A microwave oven uses the frequency of 2.45 x 10 9 Hertz (cycles/second). Calculate the wavelength of the microwave radiation used by the oven. 1 Hertz = 1 s -1 C = 3.00 x 10 8 m/s 0.122 m = 12 cm 9 Energy Relationships E = h ν Planck’s Constant, 6.626 x 10 -34 J•sec energy of photon, J hc λ =

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4 10 So the color of light depends on the wavelengths of which it is composed. 11 Do you see a cyan after image? 12 White light Spectrum The colors that combine to form white light are red, orange, yellow, green, blue, indigo, and violet (ROYGBIV) The different colors have different wavelengths and frequencies Shortest wavelength ( λ ) & highest frequency ( ν ) = violet Longest λ & lowest ν =red
5 13 Elemental Electromagnetic Fingerprints or Line Spectra If you energize gaseous elements like hydrogen gas and then diffract the light given off by the excited element you see an electro-magnetic spectrum in the visible range 14 Line Spectrum of Hydrogen discrete energy levels 15 Every element, when excited, can emit light, which contains only certain wavelengths, giving each element a unique spectrum of lines.

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6 16 Flame Tests for Metals Movie Section 6.2, 3 17 Line Spectra /Atomic Structure Relationship How do we explain the fact that each element is capable of emitting its own characteristic wavelengths of radiation (light)? Is there some connection between the wavelengths an element emits and its atomic structure? 18 Rutherford’s Atom “The Planetary Model” Section 7.4 Electrons orbiting in circular orbits at arbitrary distances from the nucleus. There were no energies or distances that were disallowed for this model of the atom. e - e-
7 19 Quantum Theory Max Planck changed the face of science. He developed a new theory that is the basis of modern physics Quantum Theory Planck assumed that energy, instead of being given off continuously, is given off in little packets, or quanta. The word quantum means a fixed amount Think of it as bundles or flashes of energy Also called photons 20 Quantum Theory Planck’s idea was that one quantum of energy (light) was related to its frequency by the equation: E = h ν The constant h (planck’s constant) has a value of 6.6262 x 10 -34 J•s, E is the amount of energy, and ν is the frequency of the radiation.

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## This note was uploaded on 11/11/2009 for the course CHEM 1341 taught by Professor Compton during the Spring '08 term at Texas State.

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Chapter 6 - 1 2 3 What is light Light is a combination of...

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