Ultraviolet radiation of 6.2 eV falls on an aluminium surface (work - function = 4.2 eV). The kinetic energy in joule of the fastest electrons emitted is

Options

A. `3.2 xx 10^(-21)`
B. `3.2 xx 10^(-19)`
C. `3.2 xx 10^(-17)`
D. `3.2 xx 10^(-15)`

Answer

B

Explanation

`K_(max) (eV) = E (eV) - W_(0) (eV) = 6.2 - 4.2 = 2 eV`
`:. K_(max) (Joules) = 2 xx 1.6 xx 10^(-19) J = 3.2 xx 10^(-19) J`