Why does a piece of red paper turn black when blue light is shone on to it?

Question

Why does a piece of red paper turn black when blue light is shone on to it?

Answer 1

it is red in white light because it reflects red and absorbs all other colors.  Take the red out of the light source and nothing is reflected.  The paper appears black.

Answer 2

Photons (traveling at the speed of light!) strike the paper and interact with the electrons orbiting atoms and molecules within the paper.  The electrons are kicked up into higher more energetic orbits but release one or more new photons in one or more steps back to their rest orbits.  Blue photons shined on red paper would all be absorbed by electrons and none would be re-released as red photons to reach your eye.  They may be re-released as infrared or UV that can't be seen and the paper would look black.

Answer 3

Things around us appear as certain colors because of the colors (i.e., wavelengths of light) that they reflect.  A red piece of paper appears red in natural light (which contains all wavelengths) because it reflects red light (it absorbs blue and all the rest).  Under a blue light, red paper absorbs most of the wavelengths of light that is being shone on it (a blue light does not shine light in the red part of the spectrum), so it appears black.

Answer 4

You perceive the paper as being red because its chemical make up forces it to reflect red light back at you whilst absorbing the other wavelengths of the spectrum. If you only shine blue light at it, this is absorbed and there is nothing to reflect back at you, hence it looks black.