Question

The work function of sodium is 2.46 eV and its threshold wavelength is 5040 $A^0$. Then the value of universal plancks constant is (given c$=3\times {10}^8$m/s)

• A. $6.7\times {10}^{-34}Js$
• B. $6.6\times {10}^{-34}Js$
• C. $6.8\times {10}^{-34}Js$
• D. $6.5\times {10}^{-34}Js$

Answer 1

The correct option is B $6.6\times {10}^{-34}Js$

$\phi =\frac{hc}{\lambda }$
$2.46\times 1.6\times {10}^{-19}=\frac{h\times 3\times {10}^8}{5040\times {10}^{-10}}$
$h=6.6\times {10}^{-34}Js$

So, the answer is option (B).