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  • Solve! The stopping potential for the photo electrons emitted from a metal surface of work function 1.7 eV is 10.4 V. Identify the energy levels corresponding to the transitions in hydrogen atom which will result in emission of wavelength equal to th

The stopping potential for the photo electrons emitted from a metal surface of work function 1.7 eV is 10.4 V. 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

 

  • Option 1)

     n = 3 to 1

     

  • Option 2)

    n = 3 to 2

  • Option 3)

    n = 2 to 1

     

  • Option 4)

    n = 4 to 1

 

Answers (1)

 

Stopping Potential /Cut-off Potential -

It is defined as the potential necessary to stop any electron from reaching the other side.

-

 

 

Conservation of energy -

h\nu = \phi _{0}+\frac{1}{2}mv^{2}_{max}

h\nu = h\nu _{0}+\frac{1}{2}mv^{2}_{max}

 

h\left ( \nu-\nu _{0} \right )=\frac{1}{2}mv^{2}_{max}

where, h - Plank's constant\ \nu - Frequency\ \nu_{0} - threshold\ frequency\ \phi_{0}- work function

- wherein

 

 eV_{s}=K.E. - \phi .-(i)

\because V_{s}= stopping potential

\Rightarrow 10.4 =K.E-1.7

\therefore K.E = 12.1 ev

This energy can be provided by the transition of an electron from n=3 to n=1

As

 \\ \Delta E = 13.6 (\frac{1}{12}-\frac{1}{9})=12.1 ev \\ 3\rightarrow 1

 


Option 1)

 n = 3 to 1

 

Correct option

Option 2)

n = 3 to 2

Incorrect option

Option 3)

n = 2 to 1

 

Incorrect option

Option 4)

n = 4 to 1

Incorrect option

Posted by

Vakul

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