Respuesta :
As per Einstein's Photo electric effect theory
[tex]E = \phi + KE[/tex]
the energy which incident in form of photon will be absorbed by the metal surface and some of the energy is released in form of KE of ejected electrons
[tex]E = 4.3 eV[/tex]
[tex]\phi = 2.2 eV[/tex]
now from the above equation
[tex]E = \phi + KE[/tex]
[tex]4.3 = 2.2 + KE[/tex]
[tex]KE = 2.1 eV[/tex]