chap9 - Chapter 9 Tro Electrons in atoms Electromagnetic...

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Chapter 9 Tro Electrons in atoms

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Electromagnetic Radiation Visible light is but one form of radiation. Wave-particle duality of light. Photons (mirror, photoelectric effect, Newton, Einstein) versus waves (prism, diffraction and interference, Huygens, Maxwell). Einstein made a very simple connection: E=hh& &where the Greek letter h (pronounced “new”) denotes the frequency of the radiation and E is the energy of the photon. h is a proportionality constant (Planck’s constant). Wavelength: h=c/h&&c is the speed of light, a constant equal to 3.0x10 8 m/s. The continuous electromagnetic spectrum.

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Electromagnetic Radiation light is one of the forms of energy technically, light is one type of a more general form of energy called electromagnetic radiation electromagnetic radiation travels in waves every wave has four characteristics that determine its properties – wave speed, height (amplitude), length, and the number of wave peaks that pass in a given time
Electromagnetic Waves velocity = c = speed of light its constant! = 2.997925 x 10 8 m/s (m•sec -1 ) in vacuum all types of light energy travel at the same speed amplitude = A = measure of the intensity of the wave, “brightness” height of the wave wavelength = λ = distance between crests generally measured in nanometers (1 nm = 10 -9 m) same distance for troughs or nodes frequency = ν = how many peaks pass a point in a second generally measured in Hertz (Hz), 1 Hz = 1 wave/sec = 1 sec -1

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Electromagnetic Waves
7 Low Frequency Wave High Frequency Wave λ λ λ

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Particles of Light scientists in the early 20 th century showed that electromagnetic radiation was composed of particles we call photons Max Planck and Albert Einstein photons are particles of light energy each wavelength of light has photons that have a different amount of energy the longer the wavelength, the lower the energy of the photons
The Electromagnetic Spectrum light passed through a prism is separated into all its colors - this is called a continuous spectrum the color of the light is determined by its wavelength

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Electromagnetic Spectrum
Light’s Relationship to Matter Atoms can acquire extra energy, but they must eventually release it When atoms emit energy, it always is released in the form of light However, atoms don’t emit all colors, only very specific wavelengths in fact, the spectrum of wavelengths can be used to identify the element

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Emission Spectrum
Spectra

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14 656.3 486.1 434.1 410.2 Absorption Spectrum Emission Spectrum Absorption Spectrum Emission Spectrum
Discrete Spectra - Quantization Atomic emission and adsorption spectra are lines occurring at specific frequencies. The lines are quantized. What else is quantized? (stairs versus ramp) Standing waves are also quantized.

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This note was uploaded on 04/11/2008 for the course CHE 101 taught by Professor Churchhill during the Fall '08 term at SUNY Buffalo.

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chap9 - Chapter 9 Tro Electrons in atoms Electromagnetic...

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