In the arrangement shown in figure y = 1.0 mm, d = 0.24 mm and D = 1.2 m. The work function of the material of the emitter is 2.2 eV. Find the stopping potential V needed to stop the photocurrent.
Given, y=1mm
∴ Fringe width y=2× 1 =2mm
d=0.24mm
D =1.2m
Work function Ф =2.2eV
We know that fringe width 
∴ 
Putting the values in above equation we get,
We also know that 
[h=
]
From Einstein’s photoelectric equation,
Stopping potential 
1