As in, when you have a red light, the light is literally red — but when you have clothing that is dyed red, it’s reflecting red light. I thought originally that objects “reflected” color by their electrons absorbing all other colors and then emitting the color it was reflecting (in this case, absorbing all other wavelengths and emitting red). But then how does this set the object aside from a light source?
In: Physics
You are correct. The difference is that the red pigment doesn’t emit light unless there is light of the correct color shining upon it. When blue light hits a red object, it just gets absorbed and turned into vibrational energy. When red light hits a red object, the red light is briefly absorbed by the object’s electrons, then red light is reemitted back out. But if there is no red light shining on the object, the electrons don’t spontaneously emit red light. On the other hand, a red light source will emit red light on its own.
As you pointed out, there are 2 “types of colour”. The substractive colors (pigment) absorb some wavelenght and makes you see the not absorbed colours. The additive (light) is a sum of different colours emited.
If you have a red light, it’s because it only emits red wavelenght (or that the other are not bright enough to be properly analysed).
If you have a red pigment, it will absorb at least blue and green light, thus appearing red. Now, is the shirt red in the dark? Well I’d say no, as it don’t reflect red light. And even more technically, if you have a red shirt in a room that is lighted with blue and green light, it will be gray/black.
And finaly, there are 2 types of pigment, the minerals and the organic ones. In Chemestry, an organic molecule is a molecule that have a carbon atome linked to an hydrogene atom. Every other molecule is mineral. Both of them absorb the photons with their electrons and will vibrate while emiting another photon (usually of another wavelenght). That’s what cause them to see them in a colour or another.
Red light generates only the wavelength that we perceive as red.
Red pigment absorbs all visible wavelengths except for the wavelength we see as red.
Latest Answers