Hi, I need a quick bit of help for an approximation/expansion used in a paper by Rolf Landauer (1950). The paper deals with the WKB method (Quantum Mechanics) but that is irrelevant to my question. There is an approximation presented as follows:(adsbygoogle = window.adsbygoogle || []).push({});

A = 1 - (K/2a)

K = a - b

If a>>K, then A will be given by:

A = (b/a)^(1/2), to the first order in K

How is this approximation made? This is the entirety of the information provided: it is at the very start of the paper.

I've change a couple variable names (a and b are infact k1 and k2, the propogation constants in a potential well, if anyone is interested). A is the transmission coefficent of a wavefunction. I appreciate any help!

Cheers

Chris

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# Confused on a Certain Approximation/Expansion

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