Final answer:
The [Cr(NH3)6]3+ complex with strong-field ligands absorbs light of the shortest wavelength compared to the other given chromium complexes, which correspond to higher energy photons.
Step-by-step explanation:
The student's question concerns the absorption of light by different chromium complexes and which absorbs light of the shortest wavelength. The key concept here is that the energy of a photon of light is inversely proportional to its wavelength. A shorter wavelength corresponds to higher energy absorbed.
Among the options provided, complexes with strong-field ligands, such as ammonia (NH3) and ethylenediamine (en), tend to have a larger splitting energy (Δ) and therefore absorb light at shorter wavelengths (higher energy) relative to weak-field ligands like water (H2O) and chloride (Cl-). Hence, [Cr(NH3)6]3+ and [Cr(en)3]3+ complexes with strong-field ligands will absorb higher energy photons (shorter wavelengths) than others. Considering this information, option b [Cr(NH3)6]3+ typically absorbs the light of the shortest wavelength and would likely be the correct answer.