Assuming that all the blackbody radiation is emitted at this wavelength

Question: Consider a metal that is being welded

Assuming that all the blackbody radiation is emitted at this wavelength (a crude approximation), how many photons does a square centimeter of the metal emit per second?

Solution: Using stefan-boltzmann law, energy emitted by blackbody
E = σAtT^4
A = 1 cm^2 = 10^-4 m^2
t = 1s
but E =hcn/λ
σ = 5.67 * 10^-8
T = b/λ = 2.898 * 10^-3/λ
n = λσAtT^4/hc
n = 5.6710^-810^-41(2.89810^-3)^4/(6.6310^-34310^8(49010^-9)^3)
n= 1.71*10^22 photons

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