Hi everybody, I would like to use the 'cauchy dispersion formula', ie (http://en.wikipedia.org/wiki/Cauchy's_equation): eta = A + B / w² Where : eta is the resulting IOR A is the base IOR B is the dispersion coefficient expressed in squarre meter (m²) w is wavelength expressed in micro-meters I try to apply this formula this way : B = 0.013 in micro-meters, A = 1.72 So first, 1) I convert the B parameter from micro-meter to m² : B = B / 1000000 2) I convert my wavelenght from nm to micro-meter : wv = 500 / 1000 But the result I got seems incorrect, I got no dispersion !!! Maybe there is a problem with my units ?
I think you mean to convert B's units from m^{2} to (μm)^{2}. For that, you have to multiply by 1000000^{2}, not 1000000.
Thanks for your answer, But based on the formula here :http://en.wikipedia.org/wiki/Cauchy's_equation the C parameters (I use B instead) is expressed in micro-meters !!!! So, if C = 0.013 in micro-meters I have to convert it to meters to use the Cauchy formula... ... then I "divide" by 1000000² ? Or there is something wrong in what I do or my units ? Thanks
OK, I see now. I didn't look at the Wikipedia page to see where the numbers came from before. If your B (their C) is already in units of (μm)^{2}, and you've converted your wavelength λ to μm, then the quantity B / λ^{2} = 0.013 / 0.5^{2} has units of (μm)^{2}/(μm)^{2}, i.e. it's unit-less, as it should be because the index of refraction is unit-less. Why do you want to convert B to m^{2}?
I see... It is just that I have see somewhere that the C parameter has to be in m²... but it seems false ! Thanks for your help