;+ ; NAME: ; ph2watt ; ; PURPOSE: ; return irradiance in watts/m^2/nm given photons/cm^2/sec ; ; CATEGORY: ; web ; ; CALLING SEQUENCE: ; ph2watt ; ; INPUTS: ; wave - array of wavelengths in nm ; irr_ph - array of irradiances in photons/cm^2/sec ; ; OUTPUTS: ; irr_w - array of irradiances in watts/m^2/nm ; ; COMMON BLOCKS: ; none ; ; MODIFICATION HISTORY: ; 02-17-03 DLW Original file creation. ; ;idver='$Id: ph2watt.pro,v 6.0 2003/03/05 19:32:43 dlwoodra Exp $' ; ;- function ph2watt, wave, irr_ph if n_params() ne 2 then begin print,' Usage: irr_w = ph2watt( wave, irr_ph )' print,' where' print,' wave is the wavelength in nm (vector or scalar)' print,' irr_ph is irradiance in photons/cm^2/second (same length)' print,' irr_w is irradiance in watts/m^2/nm (same length as inputs)' return,-1 endif if n_elements(wave) ne n_elements(irr_ph) then begin print,' ERROR: wave and irr_w have different number of elements' return,-1 endif ;energy conversion factor = Planck's constant * speed of light in vaccum PLANCK_CONSTANT = 6.626069d-34 ; J - sec SPEED_OF_LIGHT = 2.997924d8 ; m / sec HC_PRODUCT = PLANCK_CONSTANT * SPEED_OF_LIGHT / 1.d-9 ; J - nm phcms=(1d-4)/HC_PRODUCT ;times lambda conv=wave*phcms return, irr_ph/conv end