Why does a cup of hot coffee cool off how do they

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Unformatted text preview: m? – Why does an ice cube melt in a warm room? – Why does a cup of hot coffee cool off? – How do they know the ambient temperature? – This will happen even in a perfect vacuum Judah Levine, 2170L11 9 Thermal Equilibrium - 2 All bodies continuously absorb and emit energy as electromagnetic waves – Emission proportional to temperature – Thermal motion of charges in the material Body reaches thermal equilibrium when incident energy balances emitted energy Judah Levine, 2170L11 10 Body in thermal equilibrium Incident energy is either reflected or absorbed Absorbed energy is then used to drive the emission process The best emitter is therefore the best absorber A perfect emitter would be a perfect absorber A perfect absorber reflects nothing and is therefore black A “black body” is the best possible emitter Judah Levine, 2170L11 11 Black Body spectrum - 1 Radiation is generated by thermal motion of charged particles in the material Electromagnetic radiation caused by accele...
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This note was uploaded on 01/29/2014 for the course PHYSICS 2170 taught by Professor Judahlevine during the Spring '13 term at Colorado.

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