A deflection magnetometer is placed with its arm along the east-west direction ( tan   A position) and a short bar magnet is placed symmetrically along its axis at some distance with its north pole pointing towards east. In this position the needle of the magnetometer shows a deflection of 60 ° . If we double the distance of the bar magnet, then the deflection will be

Step-by-step solution

For a short bar magnet in tan A position, μ 0 4 π 2 M d 3 = H   tanθ                     ...(i) When distance is doubled, then new deflection θ ′ is given by, μ 0 4 π 2 M 2 d 3 = H   tanθ ' ....(ii) ∴         tan  ⁡ θ ′ tan  ⁡ θ = 1 8 ⇒                 t a n   θ ′ = t a n