Question

The threshold wavelength for a metal having work function $W_0$ is ${\lambda }_0$. What is the threshold wavelength for a metal whose work function is $\frac{W_0}{2}$?

• A. $4{\lambda }_0$
• B. $2{\lambda }_0$
• C. $\frac{{\lambda }_0}{2}$
• D. $\frac{{\lambda }_0}{4}$

Answer 1

The correct option is B $2{\lambda }_0$

Work function $W_0=\frac{hc}{{\lambda }_0}$ $\cdots \left(1\right)$
If work function $\frac{W_0}{2}=\frac{hc}{{\lambda }_1}$ $\cdots \left(2\right)$
by (1) and (2)
we get ${\lambda }_1=2{\lambda }_0$