Final answer:
A smaller energy gap between HOMO and LUMO leads to longer wavelengths of light, as a lower energy difference corresponds with lower frequency and thus longer wavelength. The correct option is B).
Step-by-step explanation:
A smaller energy gap between HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) results in longer wavelengths of light being emitted or absorbed when an electron transitions between these energy levels.
According to the relationship between energy, frequency, and wavelength in electromagnetic radiation, a lower energy difference corresponds to a lower frequency, and therefore a longer wavelength, as per the equation E = hν, where E is energy, h is Planck's constant, and ν (nu) is the frequency.
Also, based on the equation c = λν, where c is the speed of light and λ is the wavelength, a lower frequency means a longer wavelength, since the speed of light is constant. Option B) is the correct one.