MATLAB: Plotting Fresnel reflection plotting

beginnerplot

Hi,

I'm new to MATLAB and I tried plotting the formula for the fresnel reflection:

R=(n_S-1)^2/(n_S+1)^2.

Here's what I did:

n_S = 1:.1:3.5;
R=((n_S-1).^2)/((n_S+1).^2);

Unfortunately that gave me a number as answer (0.2235) and not the 26-Element Array I was expecting. I also tried calculating both the upper and lower part of the quotient separately. Both gave me an Array, but when I calculated R=R_upper/R_lower I still got 0.2235.

Can anyone please tell me, what I am doing wrong?

Thanks in advance for your help.

Best Answer

If anyone needs to know the answer to this. It is because he is not doing element wise division

R=((n_S-1).^2)/((n_S+1).^2);

should be

R=((n_S-1).^2)./((n_S+1).^2);

Note the './' instead of '/' for division

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MATLAB: Fresnel functions, with vectors

You only need to make one ‘hard’ modification to vectorise your function, that being the last line. Otherwise, use the vectorize (link) function, with the str2func (link) function to allow your function to be compatible with vector inputs:

function y = fresnelS(f,x,n)
    f = str2func(vectorize(f))
    if mod(n,2) == 1
        error('The number of strips must be even!');
    end
    h = x/n;
    y = f(x);
    for k = 1:2:n
        y = y + 4*f(k*h);
    end
    for k=2:2:n-1
        y = y + 2*f(k*h);
    end
    y = y.*h/3;
end

Calling it as:

n = 42;
y1 = fresnelS(@(x) sin(x^2), [3 2 1], n)

produces:

y1 =
         0.773589281078057          0.80477821467003         0.310268275967617

Success!

Best Answer

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