Question

Threshold wavelength for photoelectric effect on sodium is 5000 Å. Its work function is

• A. 15 J
• B. $16\times {10}^{-14}J$
• C. $4\times {10}^{-19}J$
• D. $4\times {10}^{-81}J$

Answer 1

The correct option is C $4\times {10}^{-19}J$

$W_0=\frac{hc}{{\lambda }_0}=\frac{6.625\times {10}^{-34}\times 3\times {10}^8}{5000\times {10}^{-10}}J=4\times {10}^{-19}J$