Question

The work function for tungsten and sodium are 4.5 eV and 2.3 eV respectively. If the threshold wavelength $\lambda$ for sodium is Å, the value of $\lambda$ for tungsten is

• A. 5893 Å
• B. 10683 Å
• C. 2791 Å
• D. 528 Å

Answer 1

The correct option is C 2791 Å

Since $W_0=\frac{hc}{{\lambda }_0};\therefore \frac{(W_0{)}_T}{(W_0{)}_{Na}}=\frac{{\lambda }_{Na}}{{\lambda }_T}or{\lambda }_T=\frac{{\lambda }_{Na}\times (W_0{)}_{Na}}{(W_0{)}_T}=\frac{5460\times 2.3}{4.5}=2791\AA$