;+
; NAME:
;	PHOTONS_TO_ENERGY
;
; PURPOSE:
;	Convert intensity from photons [ph m-2 s-1 sr-1] to energy in SI units
;       [W m-2 sr-1]
;	
;
; CATEGORY:
;	Solar-B utilities software
;
; CALLING SEQUENCE:
;	photons_to_energy, inval, wavel, outval
;
;
; INPUTS:
;	inval:	Input intensity ([ph m-2 s-1 sr-1])
;       wavel:  photon wavelength IN ANGSTROMS!!
;
; KEYWORD PARAMETERS:
;
; OUTPUTS:
;	outval:  Intensity in SI units[W m-2 sr-1]
;
; CALLS:
;
; COMMON BLOCKS:
;
; PROCEDURE:
;
; RESTRICTIONS:
;	Input in SI, i.e. [ph m-2 s-1 sr-1]
;	Photon wavelength in ANGSTROM only
;
; MODIFICATION HISTORY:
;	07-Sep-2005: Written by Oivind Wikstol
;-
pro photons_to_energy, inval, wavel, outval

  if n_params() lt 2 then begin
    print, 'photons_to_energy, inval, wavel, outval'
    return
  endif

; define constants:
  hh = 6.62618e-34
  cc = 2.99792e8
  
  outval = inval*hh*cc/wavel

end