Q. A photoelectric surface is illuminated successively by monochromatic light of wavelength λ and $\frac{\lambda}{2}$. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface of the material is : (h = Plank's constant, c = speed of light)
A) $\frac{hc}{3\lambda}$
B) $\frac{hc}{2\lambda}$
C) $\frac{hc}{\lambda}$
D) $\frac{2hc}{\lambda}$
Explanation
[Solution] $\frac{2hc}{\lambda} - \phi = 3(\frac{hc}{\lambda} - \phi) \Rightarrow \phi = \frac{hc}{2\lambda}$. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.