Question

Light of wavelength $\lambda$ falls on metal having work function $\frac{hc}{{\lambda }_0}$. Photoelectric effect will take place only if:

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

Answer 1

The correct option is C

$\lambda \le {\lambda }_0$

Photoelectric effect takes place if energy given is more than work function

$E\ge E_{\circ }\frac{hc}{\lambda }\ge \frac{hc}{{\lambda }_{\circ }}\Rightarrow \lambda \le {\lambda }_{\circ }$