; file: wav2freq.pro ; init: May 22 2017 Rob Rutten Lent ; last: May 22 2017 Rob Rutten Lent ;+ function wav2freq,wav ; convert wavelength in mm to frequency in Hz ;- ; answer no-parameter query if (n_params(0) lt 1) then begin print,' wav2freq, wav [mm]' return,-1 endif ccgs=2.99792458D10 ; velocity of light (cm/s) wavaa=wav*1.E3*1.E4 ; mm > micron > AA airtovac,wavaa,vacaa ; air > vacuum vacmm=vacaa*1.E-3*1.E-4 ; AA > mm freq=ccgs*10./vacmm ; add nice printout if (freq gt 1.E12) then $ print,' ----- '+trimd(wav)+' mm = '+trimd(freq/1.E12)+' Thz' $ else if (freq gt 1.E9) then $ print,' ----- '+trimd(wav)+' mm = '+trimd(freq/1.E9)+' Ghz' $ else if (freq gt 1.E6) then $ print,' ----- '+trimd(wav)+' mm = '+trimd(freq/1.E6)+' Mhz' $ else if (freq gt 1.E3) then $ print,' ----- '+trimd(wav)+' mm = '+trimd(freq/1.E3)+' khz' return,freq end ; ------------------------------- test freq=wav2freq(1.3) end