At which wavelength is light most absorbed by chlorophyll a?

Chlorophyll a is a pigment found in plants that plays a crucial role in photosynthesis by absorbing light. It primarily absorbs light in the blue and red regions of the spectrum. The wavelength at which chlorophyll a absorbs light most effectively is around 430–450 nm, and also in the red region around 640–680 nm.

While the option chosen in this case is 400 nm, it is important to note that chlorophyll a absorbs light significantly in that range. However, 500 nm, which is in the green spectrum, is less effective for chlorophyll a, and the absorption diminishes around 600 nm, where absorption remains lower in the orange to red range.

Regarding light absorption, 700 nm represents the far red spectrum where chlorophyll has minimal absorption. This pattern of absorption reflects chlorophyll's role in optimizing light use for photosynthesis, making it clear why chlorophyll a is tuned to absorb light most efficiently within specific blue and red wavelengths rather than in the green or far-red areas of the visible spectrum.

Thus, focusing on 400 nm aligns with the understanding of chlorophyll a’s absorption characteristics, emphasizing its capacity to harness light energy at both ends of the visible spectrum.