Two pith balls carrying equal charges are suspended from a common point by strings of equal length, the equilibrium separation between them is r. Now the strings are rigidly clamped at half the height. The equilibrium separation between the balls now become:
As discussed in @7916
from equation (i) and (ii)
From figure (b)
from equation (iii) and (iv)
Option 1)
This answer is incorrect
Option 2)
This answer is incorrect
Option 3)
This answer is correct
Option 4)
This answer is incorrect