# Determining the binding energy in the L-shell in copper

Im having trouble grasping the following problem:

Calculate the binding energy in the L-shell for copper, if the binding energy for the K-shell is $$\ 1,439*10^{-15} J\$$.

I know that you find the answer by first finding out the energy emitted by the $$K_{\alpha}$$ and then using the following equation:

$${\frac{hc}{\lambda_L}=\frac{hc}{\lambda_K}-\frac{hc}{\lambda_K{\alpha}}}$$

So im not really out after the answer to the problem. Im out after understanding why the binding energy in the L-shell is equal to the binding energy in the K-shell minus the $$K_{\alpha}$$ emission.

Shouldn't the binding energy in the L-shell be equal to binding energy in the K-shell PLUS the $$K_{\alpha}$$ emission thus making the following equation instead:

$${\frac{hc}{\lambda_L}=\frac{hc}{\lambda_K}+\frac{hc}{\lambda_K{\alpha}}} ~?$$