The stopping potential for the photoelectrons emitted from a metal surface of work function 1.7 eV is 10.4 eV. Identify the energy levels corresponding to the transitions in hydrogen atom which will result in emission of wavelength equal to that of incident radiation for the above photoelectric effect.

Options

A. n = 3 to 1
B. n = 3 to 2
C. n = 2 to 1
D. n = 4 to 1

Answer

A

Explanation

If incident radiation has wavelength `lambda`, then
`eV_(0)=(hc)/(lambda)-phi_(0)" or "(hc)/(lambda)=10.4 +1.7 = 12.1eV`
`"or "lambda=(1240eV-nm)/(12.1eV)`

and for an excited `H_(2)` atom, energy levels are
`E_(g)=E_(i)-E_(t)=-1.51-(-13.6)=12.1eV`
So, energy of transition from n = 3 to n = 1 corresponds to energy of incident photons.