An atom can radiate at any time after it is excited. It is found that in a typical case, the average excited atom has a lifetime of about 10^(-8) s. That is, during this period it emits a photon and is de-excited. What is the minimum uncertainty delta-v in the frequency of the photon?
Lecturer Physics Past Papers and Syllabus / All — Multiple-choice practice
- A. 8 x 10^6 Hz
- B. None of these
- C. 8 x 10^4 Hz
- D. 8 x 10^8 Hz
Correct answer
8 x 10^6 Hz
Explanation
Explanation Using the Heisenberg Uncertainty Principle: ΔE * Δt >= h/4π where ΔE = h * Δv (energy uncertainty) and Δt = 10^(-8) s (lifetime) h * Δv * 10^(-8) >= h/4π Δv >= 1/(4π * 10^(-8)) ≈ 8 x 10^6 Hz
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