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A point Q is located on the perpendicular bisector of an electric dipole whose dipole moment is p. If Q is at a distance r from the dipole and r is much greater than the dipole size, the electric field at Q varies as

1. p⁻¹ and r⁻²
2. p and r⁻²
3. p² and r⁻³
4. p and r⁻³

Correct answer: p and r⁻³

Solution

The electric field due to an electric dipole at a point far away (where r is much greater than the dipole size) decreases with the cube of the distance (r⁻³) and is directly proportional to the dipole moment (p), which is why the correct option is p and r⁻³.

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