Question

Threshold wavelength for a metal having work function ${\omega }_0$ is $\lambda$ . Then the threshold wavelength for the metal having work function 2${\omega }_0$ is

• A. 4$\lambda$
• B. 2$\lambda$
• C. $\lambda$ /2
• D. $\lambda$ /4

Answer 1

Answer: (C)

$\lambda$ /2

Work function $=\frac{hc}{{\lambda }_T}$
so, ${\omega }_0=\frac{hc}{\lambda }$
Now work function is $2{\omega }_0$
$2{\omega }_0=\frac{hc}{{\lambda }_1}$
$2\left(\frac{hc}{\lambda }\right)=\frac{hc}{{\lambda }_1}$
${\lambda }_1=\frac{\lambda }{2}$

So, the answer is option (C).