pro john,refre,refim,rad,wavel,qabs,qext,qsca

; john calculates the size parameter (x) and relative refractive
; index (refrel) for the given material's refractive index, the ambient
; medium's refractive index, sphere radius, and free space wavelength.
; it then calls merlyn, the subroutine that computes amplitude scattering
; matrix elements and efficiencies
; refmed= (real) refractive index of surrounding medium
refmed=1d0
; refractive index of sphere= refre + i*refim

refrel=dcomplex(refre,refim)
refrel=refrel/refmed
x=2d0*3.1415926535d0*rad*refmed/wavel
merlyn,x,refrel,qext,qsca,qback,qabs,qratio
return
end