Monochromatic flux expression?

1. Feb 27, 2008

jeebs

hi, im having trouble deriving an expression for converting between monochromatic flux expressed in wavelength and in frequency units.

i think that the monochromatic flux of a star is found by

F(Δf) = ΔE / ΔtΔfΔA

F(Δλ) = ΔE / ΔtΔλΔA

where
E = energy,
t = time,
Δf = frequency bandwidth,
A = area of photon collecting surface, and
Δλ = wavelength bandwidth.

i was shown how to do this question by my tutor but i cant remember how to do it, it involved differentiation or integration i think...

thanks!!

oh, and if you take the time to answer, could you please give me an explanation, as the answer itself doesn't really teach me anything, i'm more interested in how you found that answer.

2. Feb 27, 2008

thinkies

I think you should be posting this in the homework section.