Light absorption and reflection

[maydaymalone]

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Kaplan FL says that the riboflavin appears yellow to the human eye, thus it must be reflecting wavelengths corresponding to yellow light (570-590nm) and absorbing all other wavelengths. Can someone just explain what this means? I have been trying to google this subject matter, however, I can't seem to find a good explanation. Why does it reflect the wavelength that yellow is? I would think it would absorb that?

Thanks!

 

[aldol16]

Why do you think you would see yellow light if the object absorbs it? Think about what happens when you're seeing color. Light is incident on the object. This light is of all different wavelengths. In this experiment, imagine shining white light on it, which has all different wavelengths. The object will absorb certain wavelengths. Why? Because remember, energy is quantized. How much energy an object will absorb depends on its HOMO-LUMO gap and how much energy it takes to promote an electron from HOMO to LUMO. So an object cannot absorb the full spectrum of light - it can only absorb discrete energies, which is determined by the wavelength. If it can't absorb it, the light is reflected. So what happens to the absorbed wavelengths? Well, they're mainly converted to thermal energy if the object is opaque. That's one of the reasons things will get hot if you shine a light on it for a long time (part of that is due to convection as well).

So then what do you see? Well, you can't see the absorbed wavelengths because they have been converted to heat. So you can only see what wavelengths the object reflects! So that means that a yellow object will absorb all wavelengths but yellow.

The eye also uses complementary colors so it could also be that the object is reflecting all colors but the complementary one - purple.

 

[NextStepTutor_2]

Kaplan FL says that the riboflavin appears yellow to the human eye, thus it must be reflecting wavelengths corresponding to yellow light (570-590nm) and absorbing all other wavelengths. Can someone just explain what this means? I have been trying to google this subject matter, however, I can't seem to find a good explanation. Why does it reflect the wavelength that yellow is? I would think it would absorb that?

Thanks!

you eye can only perceive the colors that hit your retina, Whatever color you are seeing, that is what your eyes are being bombarded with.

hope this helps, good luck!