Q.
The frequency of light emitted, when the electron makes transition from the level of principle quantum number n=2 to the level with n=1 is (Take, the ionization energy of hydrogen to be 13.6eV and h≃4×10−15eV−s)
As ionisation energy is 13.6eV, so its negative will be the energy of atom in ground state (n=1)
hence E1=−13.6eV
Energy in second orbit (n=1) E2=−2213.6=−34eV
When electron jumps from n=2 to n=1, then energy of photon emitted by atom ΔE=E2−E1 =−3.4−(−13.6) ΔE=10.2eV
So, frequency (v), hv=10.2eV v=h10.2eV=4×10−15eV−s10.2eV v=255×10+15Hz