Class19

Class19 - Chemistry 83 Technologies Based on Interactions...

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Chemistry 83 Class19 1 Technologies Based on Interactions of Matter with Electromagnetic Radiation (EMR) Technologies that provide for the wants of humans: quality and quantity of life Tro, 162 Electromagnetic radiation (emr) is energy moving through space in a wave motion Visible (Vis)
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Chemistry 83 Class19 2 How does EMR interact with matter? • When emr strikes matter, energy may be transferred to the molecules making up the matter • Energies of molecules are quantized, i.e., can only have certain values called energy levels – If the amount of energy absorbed is sufFcient to change the energy level of the molecule, the added energy causes changes in some kind(s) of motions associated with the molecule – If the amount of energy absorbed is insufFcient to change the energy level of the molecule, the molecule does not undergo any changes and is said to be transparent to that radiation Ground state is energy at “room conditions” Excited states correspond to higher energies resulting from adding (red arrow) speciFc amounts of energy to the ground state Amount of energy added must equal the difference between the energies of the initial and Fnal states ±ollowing exposure to emr, molecules emit speciFc energies (blue arrows) and tend to return to ground state by all possible paths Energy Level Diagram Energy Absorption of energy Emission of energy 1 2 3 4 5 Ground state Excited states Quantized - can only have certain values - not continuous (Ground state) Excited states
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Class19 3 http://www.easymeasure.co.uk/webs/3/html/510/fg1.giF Nucleus of H atom is spinning and functions as a weak magnet. Science basis for using radiowaves in technologies Tro, 166 Radiowaves change alignment of nuclear magnets with an external magnetic Feld *Resonance frequency is the frequency of the radiowave that causes change in the orientation of the nuclear magnet. Depends on strength of external magnetic Feld. External magnetic Feld
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Class19 - Chemistry 83 Technologies Based on Interactions...

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