Magnetic fields at two points on the axis of a circular coil at a distance of $0.05\, m$ and $0.2\, m$ from the centre are in the ratio $8: 1.$ The radius of coil is .......... $m$

  • [JEE MAIN 2021]
  • A

    $0.2$

  • B

    $0.1$

  • C

    $0.15$

  • D

    $1.0$

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