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Question:

The surface of a metal is illuminated with 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)?

1.41 eV

1.68 eV

3.09 eV

1.51 eV

Solution:

From the photoelectric equation,
hc/λ = φ + (KE)max
1240/400 = φ + 1.68
⇒ φ = 1.41 eV