Green fluorescent protein (GFP) is a substance that was first extracted from jellyfish; variants are used to “tag” biological molecules for study. The original “wild” GFP absorbs 395-nm light, undergoing an upward transition to an excited state. Movement of a proton within the protein then excites it to 2.44 eV above the ground state. Photons emitted in the subsequent downward transition to the ground state provide a visual indication of the GFP’s location as seen in a microscope. What’s the wavelength of these photons?