Bohr Energy levels:- The energy of a revolving electron is :-
(i) Kinetic Energy, due to its revolution in the orbit.
(ii) Electrostatic Potential Energy.

The total energy E_u is the sum of kinetic and potential energies.
E_u = K_u + V_u = -
if the value of constants are placed then
E_u =

Dumb Question:- What is the significance of total energy of e^- as a negative quantity?
Ans:- Total energy as negative quantity sindicates that it is held in a stable state and energy needs to be supplied to it if electron has to be pulled out.

Dumb Question:- Where has the zero of potential energy been let ?
Ans:- The zero of electrostatic potential energy has been setup at infinity i.e. outside the bounds of atom.
If an electron moves from n_i orbit to lower n_f orbit then it lose, energy which is emitted in the form of radiations and the wavelength of such radiation is given by formula.
, Where R = Rydberg's constant = 1.097 x 10⁷ m^{- 1}

Why ??
energy of an orbit is given by E_n = -
from Bohr's postulate when an electron falls from higher orbit to lower orbit then energy of emitted radiation is given by
E = E_i - E_f =

if R = (constant)
then

Few named transitions :-
Lymen Series n = 2, 3, 4,...............
Balmen Series n = 3, 4, 5,...............
Paschen Series n = 4, 5, 6,...............
Brackett Series n = 5, 6, 7,...............
Pfund Series n = 6, 7, 8,...............
(In all these cases electron is moving down from nth orbit to concerned orbit)

• Total number of emission lines from same excited state n₁ to another state n₂ (< n₁) is given by