Q. The threshold wavelength for photoelectric emission from a material is $4800\ \mathring{\mathrm{A}}$. Photoelectrons will be emitted from the material, when it is illuminated with light from a
A) 40 W blue lamp
B) 40 W green lamp
C) 100 W red lamp
D) 100 w yellow lamp
Explanation
(a) The wavelength of blue light is $4800\mathring{\mathrm{A}}$, so material will emit photoelectrons when it is illuminated with light from a 40 W blue lamp.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.