Neco 2022 Physics Question 49

Practice objective / multiple choice question 49 from the 2022 Neco Physics examination.

Neco 2022 Physics Objective / Multiple Choice Hard Difficulty
Question 49 NECO • 2022 • PHYSICS • objective

A hydrogen atom makes a transition from the \(n=5\) level to the \(n=2\) level, emitting a photon. In the laboratory frame the photon is observed with a wavelength of \(440\ \text{nm}\) because the source is moving away from the observer.\n\n(a) Using the Rydberg formula, calculate the wavelength that would be observed if the source were at rest.\n(b) From the observed red‑shift, determine the speed of the source as a fraction of the speed of light (use the non‑relativistic Doppler shift \(\lambda_{\text{obs}}=\lambda_{0}(1+v/c)\)).\n(c) Compute the energy difference between the two levels in joules.

Answer Options

A. (a) \(\approx 438\ \text{nm}\) (b) \(v \approx 0.014\,c \; (\approx 4.2\times10^{6}\ \text{m·s}^{-1})\) (c) \(\Delta E \approx 4.4\times10^{-19}\ \text{J}\)
Correct Answer B. (a) \(\approx 434\ \text{nm}\) (b) \(v \approx 0.015\,c \; (\approx 4.3\times10^{6}\ \text{m·s}^{-1})\) (c) \(\Delta E \approx 4.6\times10^{-19}\ \text{J}\)
C. (a) \(\approx 440\ \text{nm}\) (b) \(v \approx 0.020\,c \; (\approx 6.0\times10^{6}\ \text{m·s}^{-1})\) (c) \(\Delta E \approx 5.0\times10^{-19}\ \text{J}\)
D. (a) \(\approx 430\ \text{nm}\) (b) \(v \approx 0.018\,c \; (\approx 5.4\times10^{6}\ \text{m·s}^{-1})\) (c) \(\Delta E \approx 4.8\times10^{-19}\ \text{J}\)
Correct Answer
B
Correct Option:
(a) \(\approx 434\ \text{nm}\) (b) \(v \approx 0.015\,c \; (\approx 4.3\times10^{6}\ \text{m·s}^{-1})\) (c) \(\Delta E \approx 4.6\times10^{-19}\ \text{J}\)

About This Question

This is Neco 2022 Physics Question 49. It is one of the objective questions from the 2022 Neco Physics examination.

Difficulty level: Hard .

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