Absorption of a photon
 Remember, the energy of a photon is Energy = h f
where f = frequency and h = Planck's constant = 6.626 x 10^{34}Js.
 The electron can make the jump from the ground level if the photon has
the frequency
f = (E_{n}  E_{1})/h
 If the atom is already excited and is in, say, the N'th level
it can jump to the n'th level if the photon has frequency
f = (E_{n}  E_{N})/h
 This process is called absorption since the
atom absorbs a photon.
 Only photons with specific frequencies can be absorbed.

