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A metal plaet of area 1\times 10^{-4 }m^{2} is iluminated by a radiation of intensity 16 mW/ m2 . The work function of the metal is 5eV . The energy of the incident photons is 10 eV and only 10%  of it produces photo electrons.The number of emitted photo electron  per second and their maximum energy, respectively,will be:

\left [1eV= 1.6\times 10^{-19 }J \right ]

 

  • Option 1)

    10^{10}\: and \: 5eV

  • Option 2)

    10^{12}\: and \: 5eV

  • Option 3)

    10^{11}\: and \: 5eV

  • Option 4)

    10^{14}\: and \: 10eV

Answers (1)

best_answer

 

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

 

 

Energy of a photon -

\fn_jvn E= h\nu = \frac{hc}{\lambda }

- wherein

h= Plank's\: constant

\boldsymbol{\nu= frequency\: of \: radiation }

\lambda \rightarrow wave \: length

 

KE_{max} = E - \phi

                =10 eV - 5eV = 5eV

\frac{n}{t} = \frac{IA}{E} = \frac{16\times 10^{-3}\times 10^{-4}}{10\times 1.6\times 10^{-18}} = 10^{11}


Option 1)

10^{10}\: and \: 5eV

Option 2)

10^{12}\: and \: 5eV

Option 3)

10^{11}\: and \: 5eV

Option 4)

10^{14}\: and \: 10eV

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