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Calculate the kinetic energy with which an electron will be emitted if 5 eV of energy is supplied to a metal surface that has work function of 2.3 eV.

Calculate the kinetic energy with which an electron will be emitted if 5 eV of energy is supplied to a metal surface that has work function of 2.3 eV. Correct Answer 2.7 ​eV

The correct answer is option 4) i.e. 2.7​ ​eV

CONCEPT:

  • Photoelectric effect: The photoelectric effect is a phenomenon where electrons are ejected from a metal surface when the light of sufficient frequency is incident on it. These ejected electrons are called photoelectrons.
    • When a photon falls on the metal surface, the photon’s energy is transferred to the electron.
    • Some part of the energy gets utilized in removing the electron from the metal surface, and the remaining goes into giving kinetic energy for the ejected electron.
  • Work function (ϕ): It is the minimum amount of energy required to cause photo-emission of electrons from a metal surface when light is incident on it.
  • Einstein’s Photoelectric Equation gives the relationship between work function (ϕ), the kinetic energy of the emitted electron, and the energy of the photon (E).

E = ϕ + KE

CALCULATION:

Given that:

Energy of incident light, E = 5 eV

Work function, ϕ = 2.3 eV

Using Einstein’s Photoelectric Equation,

E = ϕ + KE

5 = 2.3 + KE

⇒ KE = 5 - 2.3 = 2.7 eV

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