Question

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

• A. $5.6\times {10}^{-34}$Js
• B. $8.6\times {10}^{-34}$Js
• C. $7.6\times {10}^{-34}Js$
• D. $6.6\times {10}^{-34}Js$

Answer 1

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

$\varphi =\frac{hc}{\lambda };\varphi =2.46eV,\lambda =5040Angstrom,C=3\times {10}^{8}m/s$

$h=\frac{\varphi \lambda }{C}=\frac{2.46\times 1.6\times {10}^{-19}\times 5040\times {10}^{-10}}{3\times {10}^8}$

= $6.6\times {10}^3\times {10}^{-19}\times {10}^{-10}\times {10}^{-8}=6.6\times {10}^{-34}$Js