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The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68 eV. The work function of the metal is: [hc = 1240 eV.nm]

1. 1.41 eV
2. 1.51 eV
3. 1.68 eV
4. 3.09 eV

Correct answer: 1.41 eV

Solution

The work function of the metal can be calculated using the photoelectric equation, which states that the energy of the incoming photons (calculated from the wavelength) minus the kinetic energy of the ejected electrons equals the work function. Here, the energy of the 400 nm light is approximately 3.1 eV, and subtracting the kinetic energy of 1.68 eV gives a work function of about 1.41 eV.

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