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Classical Physics
Where am I going wrong (energy transfer between black bodies)?
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[QUOTE="Steve4Physics, post: 6468390, member: 681522"] [B]TL;DR Summary:[/B] Where am I going wrong (energy transfer between black bodies)? I have a problem with a very basic ‘thought experiment’. I can’t see my mistake(s) - I’m pretty sure there must be at least one! So I’m accepting likely humiliation/embarrassment and asking if anyone can explain where I’m going wrong... The surface of a black body (BB1) is at temperature T and radiates at R W/m². An ‘optical’ system collects/redirects/focuses the radiated energy from 1m² of BB1 onto a smaller black body (BB2) of area 10⁻⁴m². We now have R watts directed onto 10⁻⁴m². That’s an incident intensity onto BB2 of 10⁴R W/m². When BB2 reaches equilibrium, the power it receives (R watts) will be the same as the power it emits. So BB2 will emit R watts from an area of 10⁻⁴m². BB2’s surface is radiating at 10⁴R W/m². Since a black body's radiated power/unit area is proportional to ##T_{abs}^4## this means BB2’s temperature must be 10T. So energy is spontaneously flowing from an object at temperature T to one at temperature 10T. Err... [/QUOTE]
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Where am I going wrong (energy transfer between black bodies)?
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