According to Bohr's theory, the energy required for transition of H-atom from n=6 to n=8 is given as Δε6→8=13.6eV[
1
n12
−
1
n22
]=13.6eV[
1
62
−
1
82
] =13.6eV×0.012=0.1652eV ........(i) (a) Energy for transition of H-atom electron from n=5 to n=7. Δε5→7=13.6eV[
1
52
−
1
72
] =13.6eV×0.196 Δε5→7=0.266 Energy for transition from n=5 to n=7 is not equal to transition from n=6 to n=8. (b) Energy for transition from n=7 to n=9, Δε7→9=13.6eV[
1
72
−
1
92
] =13.6eV×0.0081=0.1096eV ∴ Energy for transition from n=7 to n=9 is not equal to transition from n=6 to n=8. (c) The transition from n=6 to n=8 has energy less than transition from n=5 to n=7. ∴ Option (c) answer is correct.