The field normal to the plane of a wire of `n` turns and radis `r` which carriers `i` is measured on the axis of the coil at a small distance `h` from the centre of the coil. This is smaller than the field at the centre by the fraction.

Options

A. `(2)/(3)(h^(2))/(r^(2))`
B. `(3)/(2)(r^(2))/(h^(2))`
C. `(3)/(2)(h^(2))/(r^(2))`
D. `(2)/(3)(h^(3))/(r^(2))`