All electrons ejected from a surface by incident light of wavelength 200nm Can be stopped before travelling 1m in the direction of uniform electric field of  4N/C.  The work function of the surface is 

The electron ejected with maximum speed  $v_{\max }$  are stopped by electric field $E=4N/C$ 
After travelling a distance d=1m
 $\frac{1}{2}m{v}_{\max }^2=eEd=4eV$
The energy of incident photon=  $\frac{1240}{200}=6.2eV$
From equation of photo electric effect
 $\frac{1}{2}m{v}_{\max }^2=hv-{\varphi }_0$
 $\therefore {\varphi }_0=6.2-4=2.2eV$