Question

If the binding energy of electrons in a metal is $250{\text{kJmol}}^{-1}$ then, the threshold frequency of the metal is:

• A. $3.8\times {10}^{38}{\text{s}}^{-1}$
• B. $3.8\times {10}^{35}{\text{s}}^{-1}$
• C. $6.2\times {10}^{11}{\text{s}}^{-1}$
• D. $6.2\times {10}^{14}{\text{s}}^{-1}$

Answer 1

The correct option is D $6.2\times {10}^{14}{\text{s}}^{-1}$

Binding energy $=250{\text{kJ mol}}^{-1}$
$=\frac{250\times {10}^3}{6.023\times {10}^{23}}=4.15\times {10}^{-19}J$ per electron
Also, binding energy $=h{v}_0$
where $v_0$ is the threshold frequency
$h{v}_0=4.15\times {10}^{-19}$
$v_0=\frac{4.15\times {10}^{-19}}{6.6\times {10}^{-34}}=6.3\times {10}^{14}{\text{s}}^{-1}$