Question

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

• A. λ > λ₀
• B. λ > 2λ₀
• C. λ < λ₀
• D. λ < λ₀/2

Answer 1

The correct option is C

λ < λ₀

So photo electric effect will only be shown if the energy of each photon is more than the work function.

Wavelength of light used is $\lambda$

So energy of each photon is$\frac{hc}{\lambda }$
Now this should be greater than work function

$\frac{hc}{\lambda }\ge \frac{hc}{{\lambda }_0}$

$\Rightarrow \lambda \le {\lambda }_0$