Centripetal force = qvB = mv²/r → r = mv / (qB). Plug in: r = (9.1 × 10⁻³¹ × 2 × 10⁶) / (1.6 × 10⁻¹⁹ × 0.5) = (1.82 × 10⁻²⁴) / (8 × 10⁻²⁰) = 2.275 × 10⁻⁵ m = 22.75 μm. - Portal da Acústica