Answer:
The indices x,y, and z not showing but lets assume T =ka^x S^y y^z
Dimension of a the radius is L
dimension of density is ML^-3
dimension of surface tension(F/L) is MT^-2
dimension of period is T
T =ka^x S^y y^z
T = L^x (ML^-3)^y (MT^-2)^z
T = L^x M^yL^-3y M^zT^-2z
M^0 L^0 T^1 = L^(x-3y) M^(y+z) T^(-2z)
T^1 = T^(-2z)
1 = -2z
==> z = -1/2
M^0 = M^(y+z)
y + z =0
y = -z
y = -(-1/2)
y = 1/2
L^0 = L^(x-3y)
x - 3y = 0
x = 3y
x = 3(1/2)
x = 3/2
Thus, x = 3/2, y = 1/2 and z = -1/2
The relationship for T
T = ka^(3/2) S^(1/2) y^(-1/2)