He atom can be excited to Is12p1 by λ=58.44nm. If lowest excited state for He lies 4857cm−1 below the above. Calculate the energy of the lower excitation state.
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Solution
E1=hcλ1=124258.44=21.25eV
For lowest excitation state λ2=1485700=2.05×10−6m=2050nmE2=12422050=0.606eV
If lowest excitation state lied 0.626eV below the 21.25eV
Energy of lowest excitation state=21.25−0.606=20.644eV