Which of the following wavelengths of light is least absorbed by chlorophyll a?

Chlorophyll a is the primary pigment involved in photosynthesis, and it plays a crucial role in absorbing light energy to drive the synthesis of organic compounds. The absorption spectrum of chlorophyll a indicates that it effectively absorbs light primarily in the blue (around 430 nm) and red (around 662 nm) regions of the spectrum, while it reflects and transmits light in the green portion (around 500 nm).

Wavelengths around 300 nm fall within the ultraviolet range, where chlorophyll does not absorb efficiently. The wavelengths near 400 nm fall in the violet-blue range, where chlorophyll shows significant absorption. The 500 nm wavelength, on the other hand, is near the green spectrum, which is least absorbed by chlorophyll a, as chlorophyll reflects green light and does not utilize it for photosynthesis.

When examining 700 nm, this wavelength falls within the far-red region, where chlorophyll a does show some absorption but not as effectively as the blue and red regions. Therefore, 500 nm is indeed the wavelength of light that chlorophyll a is least absorbing compared to the others listed, as it corresponds to the green light that chlorophyll primarily reflects and does not utilize effectively in photosynthesis.