Why do non-red objects reflect red laser light?

The color of things explained as "Objects reflect in the color that we see them, and absorb other colors."

enter image description here

But if to illuminate, say, a yellow thing with a red laser, one can clearly see the red reflected color.

How is this consistent with the fact that only yellow should be reflected by this thing, and red should be absorbed? It turns out that the yellow object is still able to reflect red.

I want to get more deep iformation about reflection of light.


1 Answer 1


When light is reflected from objects with a well defined colour, we perceive the reflected light as this colour because it reflects this colour. But the truth is that other wavelengths are also reflected, but less of it. The absorption of light is typically $\alpha < 1$ but still $\alpha_{yellow} \gg \alpha_{green}$ for example. Our eyes perceive the colour typically as that of the most dominant wavelength.

When we shine a laser on something, the light contained within the laser is the light that is reflected, even though it is reflected by a fraction of what the colour of the object would be reflected. White light contains typically all wavelengths and thus we can "sort out" the colour of the object and perceive it as this. But with a laser, photons emitted by laser are the ones that reach our eyes most of the times, and thus we see the colour of the laser. Depending on the laser wavelength and the objcet illuminated, other colours may be perceived if the object absorbs and then re-emits the energy in different wavelengths.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.