# Matlab Limitation?

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Alex on 15 Feb 2012
Edited: Mathias on 13 Oct 2013
Hey all, I've been performing some calculations with Matlab, and I've been getting unexpected results. I've been trying to calculate reflectance (R) of materials using this Fresnel equation:
R=(((n0-(n-1i.*k))./(n0+(n-1i.*k)))+(((n-1i.*k)-(n2-1i.*k2))./((n-1i.*k)+(n2-1i.*k2))).*(exp(-2.*1i.*(2.*pi./y).*(n-1i.*k).*120))./(1+((n0-(n-1i.*k))./(n0+(n-1i.*k))).*(((n-1i.*k)-(n2-1i.*k2))./((n-1i.*k)+(n2-1i.*k2))).*(exp(-2.*1i.*(2.*pi./y).*(n-1i.*k).*120))))
But all the answers I'm getting aren't what they should be (we're running a test with known values. If you want to give it a try, the values that we're currently using are as follows:
y = 250
n0 = 1
n = 1.61
k = 0
n2 = 1.69
k2 = 3.67
R = .5 (or somewhere around there)
But the answer I get is R = .092.
So, is Matlab incapable of performing such a calculation, or is there something that I can do differently go get this to work? I'd love to hear your thoughts on this one.
Thanks.

John D'Errico on 15 Feb 2012
Is it incapable? No. Have you written it out correctly? How can we even guess? What are the odds that as long a line as that, you have made a typo? I will point out that you do NOT get 0.092. You get a complex result.
R = 0.092354 - 0.74233i
My guess is you have a typo.
Walter Roberson on 15 Feb 2012
complex conjugate, or the magnitude?