The work function for potassium and cesium are $2.25$ eV and $2.14 e V$ respectively. Will the photoelectric occur for either of these elements : (a)with incident light of wavelength $5650$ A.U. and (b)with light of wavelength $5180$ A.U.?

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Solution

Photoelectric effect takes place when energy of the incident photon is greater than work function of the metal.
Energy of incident photon $E = \frac{12400}{λ (i n A^{o})} e V$
(a) : Energy of photon $E = \frac{12400}{5650} = 2.2 e V$
So, potassium will not show photoelectric effect whereas cesium will show.
(b) : Energy of photon $E = \frac{12400}{5180} = 2.4 e V$
So, both will show photoelectric effect.

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The work function for potassium and cesium are 2.25eV and 2.14eV respectively. Will the photoelectric occur for either of these elements : (a)with incident light of wavelength 5650A.U. and (b)with light of wavelength 5180A.U.?

The work function for potassium and cesium are $2.25$ eV and $2.14 e V$ respectively. Will the photoelectric occur for either of these elements : (a)with incident light of wavelength $5650$ A.U. and (b)with light of wavelength $5180$ A.U.?