Question

The work function of a metal is $4.2eV$, its threshold wavelength will be:

• A. $4000\mathring{A}$
• B. $3500\mathring{A}$
• C. $2945\mathring{A}$
• D. $2500\mathring{A}$

Answer 1

Answer: (C)

$W_0=\frac{6.6\times 10^{-34}\times 3\times 10^8}{1.6\times 10^{-19}\times {\lambda }_0}$
$=\frac{12375}{{\lambda }_0}$
$=\frac{12375}{4.2}=2945\mathring{A}$