Magnetic field due to a ring having n turns at a distance `x` on its axis is proportional to (if `r =` radius of ring)

Options

A. `a/(a^(2) x^(2))`
B. `a^(2)/(a^(2) + x^(2))^(1//2)`
C. `(na^(2))/(a^(2) +x^(2))^(3//2)`
D. `(n^(2)a^(2))/(a^(2) + x^(2))^(3//2)`

Answer

C