Step 2: Calculate the energy of the Ka x-ray. Use the formula for energy difference: \( E_{Ka} = E_{K} - E_{L} \), where \( E_{K} \) and \( E_{L} \) are the energies of the K and L shells, respectively. Substitute the given values: \( E_{K} = -69,500 \, \text{eV} \) and \( E_{L} = -12,000 \, \text{eV} \).