Spectral irradiance E(λ): The irradiance per unit wavelength
interval at a specified wavelength.
Spectral irradiance units, W m-2 nm-1
To convert into W m-2 μm-1, multiply by 1000 (1000 E)
To convert into W cm-2 nm-1, multiply by 10-4 (10-4 E)
To convert into W cm-2 μm-1, multiply by 0.1 (0.1 E)