1. The problem statement, all variables and given/known data In my excercise book, I was given a typical diagram as that in Fig (6-7) above. And the problem statement says: The diagram presents the x-ray spectrum produced by Coolidge tube. Determine the least potential difference needed to produce the characteristic radiation. 2. Relevant equations E= hƒ = hc/λ where: h is Planck's constant, ƒ is the frequency, c is light speed and λ is the wavelength) K.E= eV 3. The attempt at a solution I really don't know how to start in this, because the diagram doesn't appear to be precise, I mean I don't know actually the precise shortest wavelength where the characteristic radiation appears in the diagram, would it be 0.07nm?! If it would be 0.07nm, I will do this: E=hc/λ=(6.625*10^-34)* (3*10^8)/ (0.07*10^-9) =2.8*10^-15 j Then, eV= E -----> V=E/e = (2.8*10^-15)/ (1.6*10^-19) =17.5 kV. But I don't think my approach is correct, so I am waiting your help.