The life time of an electron in an excited state is about 10-8 s. What is its uncertainty in energy during this time?
Correct answer: B. 1.05 x 10^-26 J
- A. 1.05 x 10^-41 J
- B. 1.05 x 10^-26 J
- C. 1.15 x 10^10 J
- D. 2.19 x 10^-40 J
Explanation
The uncertainty in energy can be determined using the energy-time uncertainty principle: ΔE = h/Δt, where h is Planck's constant (approximately 6.626 x 10-34 Js) and Δt is the time the electron spends in the excited state (10-8 s). Plugging these values into the formula, we get ΔE ≈ 1.05 x 10-26 J, which corresponds to Option B. Option A and D provide values that are too small to be realistic, while Option C presents an unrealistically large value for this context.
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Quantum theory treats electromagnetic radiation as packets of energy called photons, with energy proportional to frequency through E equals hf. The topic covers Planck's hypothesis, photon momentum, the photoelectric effect, threshold frequency, work function and wave particle duality, distinguishing quantised energy exchange from classical continuous radiation.
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