F( λ )=Φ q 1.24 λ(μm) 1 Δλ(μm)
F(λ) is the spectral irradiance in Wm-2µm-1; Φ is the photon flux in # photons m-2sec-1; E and λ are the energy and wavelength of the photon in eV and µm respectively; and q is a constant of 1.6 · 10-19
F( λ )=ΦE 1 Δλ in SI units
