question_answer

If ultra-violet radiation of 6.2 eV falls on an aluminium surface (work function 4.2 eV ), then K.E. in joules of the fastest electron emitted is approximately

A)  \[\text{3 }\times \text{ 1}{{0}^{-\text{23}}}\]

B)  \[\text{3 }\times \text{ 1}{{0}^{-\text{21}}}\]

C)  \[\text{3 }\times \text{ 1}{{0}^{-\text{19}}}\]  

D)  \[\text{3 }\times \text{ 1}{{0}^{-\text{17}}}\]