I was just searching around in my store room and I found this Fisher-Price Light Sketcher. I am just amazed how the light from the pen draws on the board without even contact! I searched a lot but couldn't find a working principle of this thing. Probably the light emitted by the pen is black light. Can you tell me how it works? Thanks! The product: https://service.mattel.com/us/productDetail.aspx?prodno=L3244&siteid=27 The text mentions that Light from the child-safe pen reacts with special ink on the product drawing surface. How does this work? And is this type of light safe for human skin?

  • $\begingroup$ I could come back to this if no other user will answer. It is uv-excited fluorescence in the visible, perhaps followed by phosphorescence. Alternatively emission from a structural change, true photochromism. Sometimes the term photochromism is used even for the first standard mechanism, especially in solid matrixes and application like this. About safety, I think we can trust Mattel and governments enough. $\endgroup$
    – Alchimista
    Oct 25 '19 at 11:55
  • $\begingroup$ Can you explain further please? $\endgroup$ Oct 26 '19 at 11:12
  • $\begingroup$ Are you familiar with fluorescence? The general principle is uv excites the molecules that after non radiative relaxations emit in the visible. Is not truly phitochromism, which should be reserved to colour changes related to the absorbing molecule adjusting its structure upon photoexcitation, thereby changing absorption spectrum. This is also possible but it should lead to a more permanent trace. $\endgroup$
    – Alchimista
    Oct 26 '19 at 13:10
  • $\begingroup$ Can you write an answer? $\endgroup$ Oct 29 '19 at 19:36

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