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title: "A pure sample of a gas is analyzed using absorption spectroscopy. The resulting spectrum shows two distinct absorption bands: Peak 1 at a wavelength of \\(\\lambda_1 = 280\\text{ nm}\\) (ultraviolet region) and Peak 2 at a wavelength of \\(\\lambda_2 = 5.8\\ \\mu\\text{m}\\) (\\(5800\\text{ nm}\\), infrared region). Which of the following statements correctly identifies the type of molecular transition associated with each peak and provides the valid physical justification?"
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url: "https://nerd-notes.com/ubq/123634/"
date_modified: "2026-09-28T12:01:52+00:00"
---

# A pure sample of a gas is analyzed using absorption spectroscopy. The resulting spectrum shows two distinct absorption bands: Peak 1 at a wavelength of \(\lambda_1 = 280\text{ nm}\) (ultraviolet region) and Peak 2 at a wavelength of \(\lambda_2 = 5.8\ \mu\text{m}\) (\(5800\text{ nm}\), infrared region). Which of the following statements correctly identifies the type of molecular transition associated with each peak and provides the valid physical justification?

A pure sample of a gas is analyzed using absorption spectroscopy. The resulting spectrum shows two distinct absorption bands: Peak 1 at a wavelength of \(\lambda_1 = 280\text{ nm}\) (ultraviolet region) and Peak 2 at a wavelength of \(\lambda_2 = 5.8\ \mu\text{m}\) (\(5800\text{ nm}\), infrared region). Which of the following statements correctly identifies the type of molecular transition associated with each peak and provides the valid physical justification?

- **A.** Peak 1 corresponds to electronic transitions and Peak 2 corresponds to vibrational excitations, because photons of wavelength \(\lambda_1\) have higher photon energy (\(E = \dfrac{hc}{\lambda}\)) corresponding to the larger quantized energy gap between electronic energy levels.
- **B.** Peak 1 corresponds to electronic transitions and Peak 2 corresponds to vibrational excitations, because photons of wavelength \(\lambda_1\) have lower photon energy that matches the weak attraction of valence electrons, whereas photons of wavelength \(\lambda_2\) have higher photon energy needed to bend and stretch covalent bonds.
- **C.** Peak 1 corresponds to vibrational excitations and Peak 2 corresponds to electronic transitions, because altering the vibrational modes of covalent bonds requires larger quanta of energy than promoting valence electrons between molecular orbitals.
- **D.** Peak 1 corresponds to vibrational excitations and Peak 2 corresponds to electronic transitions, because shorter-wavelength radiation has lower frequency (\(c = \lambda\nu\)) and thus lower photon energy, which is sufficient only to induce bond vibrations.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123634/*