Final answer:
The statement is false; in UV-Vis spectroscopy, electrons are excited from the Highest Occupied Molecular Orbital (HOMO) to the Lowest Unoccupied Molecular Orbital (LUMO) when they absorb light with energy equivalent to the HOMO-LUMO gap. The correct option is B).
Step-by-step explanation:
The statement that in UV-Vis spectroscopy, electrons are excited from LUMO to HOMO is false. In UV-Vis spectroscopy, the excitation of electrons occurs from the Highest Occupied Molecular Orbital (HOMO) to the Lowest Unoccupied Molecular Orbital (LUMO).
This is because the LUMO is the next available energy state above the HOMO where an electron can be excited to when it absorbs the energy equivalent to the HOMO-LUMO gap. Such electronic transitions can happen by absorbing light in the UV or visible range, depending on the size of the energy gap.
The wavelength of light absorbed during this transition corresponds to the energy required to promote the electron. In the case of conjugated systems, this energy gap is smaller, which results in the absorption of longer wavelengths that can even fall into the visible spectrum.
For example, the compound 1,3-butadiene, with its conjugated system, can absorb UV light with a wavelength of 217 nm. Conversely, extended pi systems like in beta-carotene can absorb light within the visible range, causing them to be colored. Option B) is the correct one.