An infinitely long wire carrying current I is along Y axis such that its one end is at point A (0, b) while the wire extends upto $+\infty .$ The magnitude of magnetic field strength at point (a, 0) is

• A

  $\frac{{\mathrm{\mu }}_0\mathrm{i}}{4\mathrm{\pi a}}\left(1+\frac{\mathrm{b}}{\sqrt{{\mathrm{a}}^2+{\mathrm{b}}^2}}\right)$

• B

  $\frac{{\mathrm{\mu }}_0\mathrm{i}}{4\mathrm{\pi a}}\left(1-\frac{\mathrm{b}}{\sqrt{{\mathrm{a}}^2+{\mathrm{b}}^2}}\right)$

• C

  $\frac{{\mathrm{\mu }}_0\mathrm{i}}{4\mathrm{\pi a}}\left(\frac{\mathrm{b}}{\sqrt{{\mathrm{a}}^2+{\mathrm{b}}^2}}\right)$

• D

  None of these