• # question_answer Ultraviolet radiations of $6.2\,eV$ falls on an aluminium surface (work function $4.2\ eV$). The kinetic energy in joules of the fastest electron emitted is approximately    A) $3.2\times {{10}^{-21}}$ B) $3.2\times {{10}^{-19}}$ C) $3.2\times {{10}^{-17}}$ D) $3.2\times {{10}^{-15}}$

 [b] ${{K}_{\max }}(eV)=E\,(eV)-{{W}_{0}}\,(eV)$$=6.2-4.2=2\ eV$ $\therefore \,\,\,\,\,{{K}_{\max }}(Joules)=$$2\times 1.6\times {{10}^{-19}}J=3.2\times {{10}^{-19}}J$