Ionised hydrogen atoms and α-particles enter perpendicular to a uniform magnetic field B with the same momentum. What is the ratio of radii of their paths r(H) : r(α)?
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Ionised hydrogen atoms and α-particles enter perpendicular to a uniform magnetic field B with the same momentum. What is the ratio of radii of their paths r(H) : r(α)?

G1 Physics · Accepted Answer

Step 1: For a charged particle entering perpendicular to B, p = |q|Br. Step 2: Hence r = p/(|q|B). If p and B are equal, r ∝ 1/|q|. Step 3: For H⁺, |q(H)| = e; for an α-particle, |q(α)| = 2e. Step 4: r(H)/r(α) = 2e/e = 2. Final answer: (D) 2:1.