Bohr–de Broglie Standing-Wave Condition (True/False) In the Bohr–Sommerfeld / de Broglie picture for quantized circular orbits, the circumference of an allowed electron orbit equals an integer multiple of the electron’s wavelength (2πR = nλ). True or false?
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ATrue
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BFalse
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CTrue only for the ground state
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DFalse unless spin–orbit coupling is neglected
Answer
Correct Answer: True
Explanation
Introduction / Context:De Broglie associated a wavelength λ = h/p with matter particles. The Bohr–Sommerfeld quantization condition can be viewed as a standing-wave requirement: only those orbits are stable where an integer number of wavelengths fits around the circumference, ensuring constructive interference and a stationary state.
Given Data / Assumptions:
- Circular orbit of radius R.
- Wavelength λ = h/p for the electron.
- Old quantum theory framework (pre-Schroedinger), used as an intuitive model.
Concept / Approach:
The standing-wave condition is 2πR = nλ for integer n. This is equivalent to quantized angular momentum L = nħ because p = m v and L = m v R; substituting λ = h/(m v) gives m v R = nħ. Thus, both the de Broglie and Bohr views are consistent for circular orbits in hydrogen-like systems.
Step-by-Step Solution:
Impose standing-wave condition: 2πR = nλ.Use λ = h/p, p = m v ⇒ 2πR = n h / (m v).Rearrange to get m v R = n h / (2π) = nħ, the Bohr condition.Verification / Alternative check:
The derived energy levels E_n from this quantization match the Rydberg series for hydrogen, validating the physical picture within its domain.
Why Other Options Are Wrong:
- “False” choices contradict the established equivalence in the old quantum model.
- Ground-state-only or spin–orbit caveats are not part of the standing-wave criterion.
Common Pitfalls:
Confusing the heuristic Bohr–de Broglie model with exact quantum mechanical orbitals; the standing-wave idea is an analogy but correctly leads to L = nħ for circular motion.
Final Answer:
True