Question

If the threshold wavelength of light for photoelectric effect from sodium sodium surface is $6800\stackrel{o}{A}$ then the work function of sodium is

• A. $1.8eV$
• B. $2.9eV$
• C. $1.1eV$
• D. $4.7eV$

Answer 1

The correct option is (B) $2.9eV$

We know,

The formula for work function can be given as -

$W=\frac{hc}{{\lambda }_0}$

Putting all the values

$=\frac{6.63\times {10}^{-34}\times 3\times {10}^8}{6.8\times {10}^{-7}}$

$=\frac{19.89}{6.8}\times {10}^{-34}\times {10}^8\times {10}^7$

$=2.95\times {10}^{-19}$

$\Rightarrow 2.9eV$

Hence, the work function of sodium is 2.9 eV