(In SI units) Start with London's 2nd equation in Superconductivity, curl J = 1/(μ*λ²), and Ampere's curl B = μ*j. Then we curl both side curl curl B = μ* curl J and we do the substitution. So curl curl B = 0 - del²B which is the laplacian operator. My question is...how to integrate it? the equation becomes -del²B = -B/λ² And I am not sure how to integrate it to solve for B(x). Am I supposed to? I don't understand how the books jump to B(x) = B*exp(-x / λ) Please help and thank you very much. Any input is much appreciated too.