Question

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

• A. $\lambda >{\lambda }_o$
  
• B. $\lambda >2{\lambda }_o$
  
• C. $\lambda <{\lambda }_o$
  
• D. $\frac{1}{\lambda }<\frac{1}{{\lambda }_0}$
  

Answer 1

The correct option is C $\lambda <{\lambda }_o$


In photoelectric effect, the minimum energy required to remove an electron from a given metal surface is called as work function of the metal.
Here the work function is given as $\frac{hc}{{\lambda }_o}$
So ejections of electrons is only possible if we can provide more energy than the work function.
Again lesser is the wavelength more is the energy of the radiation.
Thus the photoelectric effect will take place only if $\lambda <{\lambda }_o$.