Question

Work function of a metal is $5.2\times {10}^{-18}J$, then its threshold wavelength will be

• A. $736.7\mathring{A}$
• B. $760.7\mathring{A}$
• C. $301\mathring{A}$
• D. $380.7\mathring{A}$

Answer 1

Answer: (D)

Given - work function of metal $W=5.2\times {10}^{-18}J$

The work function of a metal is given by ,

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

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

where ${\lambda }_0=$ threshold wavelength ,

$h=6.6\times {10}^{-34}Js$

$c=3\times {10}^{8}m/s$

Hence ,by ${\lambda }_0=\frac{hc}{W}$

${\lambda }_0=\frac{6.6\times {10}^{-34}\times 3\times {10}^8}{5.2\times {10}^{-18}}=380.7A^0$