chem1aquantumlight (1) - Quantum Mechanics: An Introduction...

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Quantum Mechanics: An Introduction Electromagnetic radiation exhibits wavelike properties which can be depicted in the following representation below: The wavelength , λ (lower-case Greek letter lambda), is represented by number 1 , or the peak-to-peak distance, and is generally in units of meters (although usually converted to nm). The number 2 represents the amplitude , or the height of the wave above/below the center line. Finally, the number 3 represents the node , or the point at which an electron occupying an orbital will NOT be found (to be discussed in more detail later). The number of cycles per second is called the frequency , denoted with the symbol ν (the Greek letter nu), and expressed in units of s -1 of Hz (Hertz). 1. 3. 2.
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Both light and waves can be characterized by wavelength and frequency, and all electromagnetic radiation moves at the speed of light ( c ). Max Planck first analyzed data from the emission of light from hot, glowing solids. He observed that the color of the solids varied with temperature. Furthermore, Planck suggested that a relationship exists between energy of atoms in the solid and wavelength. This led to the following equation: νλ = c
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νλ = c This equation has multiple interpretations. If the wavelength is long, there will be fewer cycles of the wave passing a point per second; thus, the frequency will be low. Conversely, for a wave to have a high frequency, the distance between the peaks of the wave must be small (short wavelength). In summary, an inverse relationship exists between frequency and wavelength of electromagnetic radiation as the speed of light is always constant .
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Energy can be released (or absorbed) by atoms in discreet chunks (also known as quantum or photons) of some minimum size; that is, energy is quantized and emitted/absorbed in whole number units of h ν . Collectively, we say that: E = n h = n hc/ λ where n = the quantum number, h = Planck’s constant (6.626 x 10 -34 J s), = frequency, = wavelength, and c = speed of light (3.0 x 10 8 m/s). Energy (E) is generally expressed in units of Joules (J), where this actually implies J/atom.
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Electromagnetic Spectrum Electromagnetic waves are produced by a combination of electrical and magnetic fields which are at right angles to one another (i.e. perpendicular). The various types of waves include: radiowaves, microwaves, infrared, visible light, ultraviolet, x-rays, cosmic rays, and gamma rays. All electromagnetic waves travel at the speed of light; they differ from one another by their corresponding wavelengths and frequencies. Increasing Frequency ( ν ) and Energy (E) Radio Micro IR Visible UV X-ray Cosmic Gamma Increasing Wavelength ( λ )
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L I G H T ELECTROMAGNETIC RADIATION VISIBLE LIGHT IS ORDERED AS: R R O O Y Y G G B B I I V V red red orange orange yellow yellow green green blue blue indigo indigo violet violet 700nm 400nm low energy high energy long wavelength short wavelength Example: A radiation source has a frequency of 2.35 x 10
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This note was uploaded on 12/21/2011 for the course HORT 121 taught by Professor Mcmurry during the Spring '11 term at American College of Gastroenterology.

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chem1aquantumlight (1) - Quantum Mechanics: An Introduction...

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