Question

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. $3.2\times {10}^{-15}$

Answer 1

The correct option is B

$3.2\times {10}^{-19}$

$K_{max}\left(eV\right)=E\left(eV\right)-W_0\left(eV\right)=6.2-4.2=2eV$
$\therefore K_{max}\left(Joules\right)=2\times 1.6\times {10}^{-19}J=3.2\times {10}^{-19}J$