Ultraviolet radiations of 6.2 eV falls on an aluminium surface. Kinetic energy of fastest electrons emitted is (work function = 4.2 eV)

Options

A. `3.2 xx 10^(-21)` J
B. `3.2 xx 10^(-19)` J
C. `7 xx 10^(-25)` J
D. `9 xx 10^(-32)` J

Answer

B

Explanation

`K_(max) = h upsilon - W_(0) = 6.2 eV - 4.2 eV`
`= 2.0 eV = 2.0 xx 1.6 xx 10^(-19) j = 3.2 xx 10^(-19) J`