Electron wavelength: choose your answer
Original set: 22 September 2026 · Publication edition: 24 September 2026
An electron moving with a velocity of 1.0 × 10⁶ m/s has a de Broglie wavelength closest to (mₑ = 9.1 × 10⁻³¹ kg, h = 6.63 × 10⁻³⁴ Js):
A. 7.3 × 10⁻¹⁰ m
B. 3.6 × 10⁻¹⁰ m
C. 7.3 × 10⁻⁷ m
D. 1.46 × 10⁻⁹ m
Choose before revealing the explanation.
Reveal explanation, sources and original-item counts
Answer: A — 7.3 × 10⁻¹⁰ m. At this speed, use nonrelativistic momentum p = mv.
p = (9.1 × 10⁻³¹)(1.0 × 10⁶) = 9.1 × 10⁻²⁵ kg m/s.
λ = h/p = (6.63/9.1) × 10⁻⁹ m ≈ 7.29 × 10⁻¹⁰ m.
B is about half the result, D about twice it, and C about 1000 times it. These numerical comparisons do not tell us how a learner reasoned. Keep the units in SI and check the exponent when dividing.
Exact-version September 22 group: 3 correct, 9 wrong, 7 skips. Wrong among non-skipped answers: 9/12 (75%). A 3/B 5/C 2/D 2; skips 7. Two UNKNOWN-version responses are excluded from this group.
Source: OpenStax, de Broglie’s Matter Waves
Counts account for merged accounts. Snapshot frozen September 24 08:24 IST. Accounts are not verified people; late arrivals may change counts; answer language is UNKNOWN.
The original stem and options are retained; this reviewed explanation does not claim a production-app update.
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