In absorbing 10.2 eV energy, the electron of a hydrogen atom jumps from its initial orbit to next higher energy orbit . As the electron returning to the former orbit, a photon is emitted. What is the wavelength of this photon ?

Explanation

According to Bohr's postulate,
hv=`E_i-E_f`
or, `(hc)/(lambda)=E_i-E_f or, lambda =(hc)/(E_i-E_f)`
Difference between two energy levels,
`E_i-E_f=10.2eV =10.2xx1.6xx10^(-12) erg`
`therefore lambda =(6.55xx10^(-27)xx3xx10^(10))/(10.2xx1.6xx10^(-12)) =1204 xx10^(-8)cm =1204 "Å"`