A rod of length 2L lies on the x-axis, centered at the origin, and carries line charge density λ=λ₀(x/L),where λ₀ is a constant.
(a) Find an expression for the electric field strength at points on the x-axis for x 7L.
(b) Show that for x >>L your result has the 1/x³ dependence of a dipole field, and determine the dipole moment of the rod.