An α-particle moves in a circular orbit of radius 0.83 cm in magnetic field 0.25 T. Its de Broglie wavelength is approximately:
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An α-particle moves in a circular orbit of radius 0.83 cm in magnetic field 0.25 T. Its de Broglie wavelength is approximately:

G1 Physics · Accepted Answer

Magnetic force provides centripetal force: p = qBr. For α-particle, q = 2e, r = 8.3 × 10⁻³ m, B = 0.25 T. Hence λ = h/(qBr) = 6.626 × 10⁻³⁴/[2 × 1.602 × 10⁻¹⁹ × 0.25 × 8.3 × 10⁻³] ≈ 9.96 × 10⁻¹³ m = 0.00996 Å. Answer: D.