Question 5(1 point) 4 Saved Cells of Chlamydomon as appear green under a light microscope because green photons are reflected by chlorophyll or pass right through it. What is the biophysical reason why chlorophyll cannot absorb green light? A. Green photons are too unstable to be absorbed by chlorophyll. B. Chlorophyll lacks an excited state that matches the energy of a green photon. C. Green photons of light contain too much energy; absorption would result in the oxidation of chlorophyll. D. Chlorophyll does absorb green light; the excited state just decays very rapidly with the energy being lost as heat.

The correct answer is **B. Chlorophyll lacks an excited state that matches the energy of a green photon.**<br /><br />Here's why:<br /><br />* **Chlorophyll absorbs light energy to excite electrons.** These electrons move to higher energy levels (excited states). The specific energy levels available to an electron in a chlorophyll molecule are determined by its molecular structure.<br /><br />* **Photons must have the precise amount of energy corresponding to the difference between the ground state and an available excited state in order to be absorbed.** Green light's energy doesn't match the energy gap between chlorophyll's ground state and any of its available excited states.<br /><br />* **Since green light's energy isn't absorbed, it's either reflected or transmitted,** which is why plants appear green to us.<br /><br />Let's look at why the other options are incorrect:<br /><br />* **A. Green photons are too unstable to be absorbed by chlorophyll.** Photon stability isn't a relevant factor in chlorophyll's absorption spectrum.<br /><br />* **C. Green photons of light contain too much energy; absorption would result in the oxidation of chlorophyll.** While excessively high-energy photons (like UV light) can damage chlorophyll, green light's energy is lower than the photons chlorophyll *does* absorb (red and blue).<br /><br />* **D. Chlorophyll does absorb green light; the excited state just decays very rapidly with the energy being lost as heat.** If chlorophyll absorbed green light, we wouldn't see green reflected back. The rapid decay described here happens with *absorbed* photons, but in different wavelengths, as part of the process of converting light energy into chemical energy.<br />