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re: light output of dimmed lamps
24 dec 2005
mark lloyd wrote:
>>every black body above absolute zero emits some visible light.
>
>would it always be in the limited frequency range this is visible to humans?
there would always be some visible light, but it's very faint at low temps :-)
20 pi=4*atn(1)
30 lambdau=7.8e-07'upper visible limit (meters)
40 lambdal=3.8e-07'lower visible limit (meters)
50 for lt=2 to 4'log f temp
60 tf=10^lt'temp (f)
70 tk=(tf+460)/1.8'temp (k)
80 gam=.0143879/(lambdau*tk)'pivovonsky and nagel (1961) polynomial term
90 cfracu=0'initialize upper cumulative fraction
100 for m=1 to 3
110 term=15/(pi^4)*(((m*gam+3)*m*gam+6)*m*gam+6)
120 cfracu=cfracu+exp(-m*gam)/(m^4)*term
130 next m
140 gam=.0143879/(lambdal*tk)
150 cfracl=0
160 for m=1 to 3
170 term=15/(pi^4)*(((m*gam+3)*m*gam+6)*m*gam+6)
180 cfracl=cfracl+exp(-m*gam)/(m^4)*term
190 next m
200 p=5.6697e-08*(tk^4)'total emissive power (w/m^2)
210 efrac=cfracu-cfracl'fraction of emissive power in visible spectrum
220 print tf,efrac,p,efrac*p
230 next
temp visible fraction total power visible power
100 f 6.010933e-22 531.1561 w/m^2 3.192744e-19 w/m^2
1000 2.753038e-07 24540.4 6.756065e-03
10000 .4668266 6.465423e+07 3.018231e+07
nick
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