When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is:

  • Option 1)

    0.65 eV

  • Option 2)

    1.0 eV

  • Option 3)

    1.3 eV

  • Option 4)

    1.5 eV

 

Answers (1)

Let Initial energy was E.

Then abter increasing it by 20% it becomes 1.2 E .

Let work function is  \Phi.

Then   E- \Phi = 0.5 ev ------------(1)

         1.2 - \Phi = 0.8 ev ------------(2)

or    1.2.\left ( 0.5ev+\Phi \right )-\Phi =0.8ev

0.6ev+1.2\Phi -\Phi =0.8\:ev

or 0.2\Phi = 0.2ev

\therefore \Phi = 1ev


Option 1)

0.65 eV

Incorrect

Option 2)

1.0 eV

Correct

Option 3)

1.3 eV

Incorrect

Option 4)

1.5 eV

Incorrect

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