Calculating Energy Difference for K Characteristic X-Ray Line of Tungsten

[MrDMD83]

Homework Statement

The K characteristic X-ray line for tungsten has a wavelength of 1.94 10-11 m. What is the difference in energy between the two energy levels that give rise to this line? Express this in each of the following units.
(a) joules
J
(b) electron volts
eV

Homework Equations

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The Attempt at a Solution

How do I find the two energy levels?

 

[JeffKoch]

You don't need to know the energy levels, you just need to know their difference in energy. You know the x-ray wavelength, and there is an equation that gives you the energy of the x-ray corresponding to this wavelength - what is that equation?