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  • Help me answer: The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately

The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately

Option 1)

540 nm

 Option 2)

400 nm
Option 3)

310 nm

 Option 4)

220 nm

Answers (1)

best_answer

As we learnt in

Work function -

Energy used to overcome the surface barrier and come out of metal surface.

\phi = h\nu _{0}

- wherein

h= Plank's \: constant

\nu _{0}= threshold \: frequency

 

 For electron to be emitted minimum energy of the photon must be 

{\phi}=\frac{hc}{\lambda}

{\lambda}=\frac{hc}{\phi}=\frac{1240}{4}nm=310\ nm

Correct answer is option 3.


Option 1)

540 nm

This is an incorrect option.

Option 2)

400 nm

This is an incorrect option.

Option 3)

310 nm

This is the correct option.

Option 4)

220 nm

This is an incorrect option.

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perimeter

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