Umakant Kondapure, Collin Fernandes, Nipun Bhatia, Vikram Bathula and, Ketki Deshpande Solutions for Chapter: Electrons and Photons, Exercise 3: Competitive Thinking

The threshold wavelength for lithium is $5250 \stackrel{\circ }{\mathrm{A}}$. For photoemission to take place, the wavelength of the incident light must be

Two identical photo-cathodes receive the light of frequencies $f_1$ and $f_2.$ If the velocities of the photoelectrons (of mass $m$ ) coming out are $v_1$ $v_2$and $v_2$ respectively, then 
 

The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three different radiations. Which one of the following is a correct statement?                                                                                                                                                                                             

A metal surface is illuminated by light of two different wavelengths $248\mathrm{nm}$ and  $310\mathrm{nm}$. The maximum speeds of the photoelectrons corresponding to these wavelengths are$u_1$ and ${\mathrm{u}}_2,$ respectively. If the ratio ${\mathrm{u}}_1:{\mathrm{u}}_2=2\because 1$ and $\mathrm{hc}=1240\mathrm{eVnm},$the work function of the metal is nearly 
 

A photon of energy E ejects a photoelectron from a metal surface whose work function is ${\mathrm{W}}_0.$ If this electron enters into a uniform magnetic field of induction B in a direction perpendicular to the field and describes a circular path of radius r, then the radius r, is given by, (in the usual notation) 
 

Light of wavelength ${\lambda }_{\mathrm{A}}$and ${\lambda }_{\mathrm{B}}$ Falls on two identical metal plates $A$ and $B$ respectively. The maximum kinetic energy of photoelectrons is ${\mathrm{K}}_{\mathrm{A}}$ and $K_B$ Respectively, then which one of the following relations is true? $\left({\lambda }_{\mathrm{A}}=2{\lambda }_{\mathrm{B}}\right)$ 
 

The energy of the em waves is of the order of $15 \mathrm{keV}.$ To which part of the spectrum does it belong ?
 

Relation between the stopping potential ${\mathrm{V}}_0$ of a metal and the maximum velocity of the photoelectrons is