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enter image description here

In the first image, the laser colour is green.

When it is shined on the plastic cap of the pink highlighter, the colour changes, why has this happened?

Tech Details about the Laser Source are; Max output <1mW Wavelength 532nm +_10

Class II laser productenter image description here


marked as duplicate by gigacyan, ACuriousMind, Sebastian Riese, Ryan Unger, John Rennie Sep 16 '15 at 14:04

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  • $\begingroup$ What happens when you shine the laser at the edge of the two surfaces? Does half of the point show up as "yellow" and the other half show up as "green"? $\endgroup$ – a CVn Sep 16 '15 at 10:57
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    $\begingroup$ The laser induces fluorescence in the plastic cap, which occurs at longer wavelength. This question has already been answered here: physics.stackexchange.com/questions/72560/… $\endgroup$ – gigacyan Sep 16 '15 at 11:19

You are almost certainly seeing fluorescence here. Even 532nm is still a fairly short wavelength as far as fluorophores are concerned and many fluorophores commonly used to color plastics absorb powerfully at 532nm. For example, rhodamine B has an absorption peak near 532nm, and it fluoresces strongly in red yellow. Indeed, if you see the Wikipedia Page for Rhodamine B there is a picture of a 532nm laser lighting a rhodamine B solution, and the red/ orange/yellow fluorescence gives an effect almost identical to what you are seeing.

You are almost certainly seeing yellow/orange/red fluorescence mixed with scattered 532nm light.

This doesn't prove that rhodamine B is in the plastic - I know nothing about whether it could survive the production processes for plastic (I suspect it would not) - but the point is that there are many fluorophores that would show exactly the kind of behavior you are seeing.

  • $\begingroup$ If 2 lasers of different colour intersect, what will be happening at the point of intersection? Won't colour mixing happen?? Won't that point where the lasers intersect be of different colour? For example if we use a green and a red laser then will not the point of intersection be yellow, if we use red and blue will not the point of intersection be magenta? $\endgroup$ – g g Sep 18 '15 at 12:59
  • $\begingroup$ @gg You will see a mixture of the two scattered colors, together with the fluorescence. $\endgroup$ – WetSavannaAnimal Sep 18 '15 at 13:22

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