Q. The work function ( ) of some metals is listed below. The number of metals which will show photoelectric effect when light of 300 nm wavelength falls on the metals is :
Metakl Li N K Mg Cu Ag Fe Pt W
2.4 2.3 2.2 3.7 4.8 4.3 4.7 6.3 4.75

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Solution:

Energy of photon

For photoelectric effect to occur, energy of incident photons, must be greater than work functions of metal. Hence, only Li, Na, K and Mg have work functions less than 4.14 eV.