How exactly does a mood ring work?

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Mood rings operate using liquid crystal structures that expand and contract with temperature changes, affecting which wavelengths of light are reflected. Wavelengths that do not match the specific conditions are either absorbed or transmitted, typically absorbed by a black backing material. The color change in mood rings is a result of thermochromic elements reacting to body temperature. For deeper insights into the absorption process, resources like the Wikipedia article on electromagnetic radiation absorption are recommended. Understanding these principles clarifies how mood rings function and why they may appear dark when not in use.
Edi
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Ok, I understand that the liquid crystal structure expands and contracts in response to thermal fluctuations and that the structure is made of layers... and only the wavelengths that mach exactly or are half (or quarter and so on) can have constructive interference, thus, only those wavelengths are supposed to be reflected from the ring/ crystal structure... BUT - what happens to all the other wavelengths, that do not mach those certain lengths at specific temperature? .. yes, they do not act in constructive interference, but .. where do they go/ why are they absorbed?
 
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They are absorbed or transmitted.
 
Well. that explains pretty much nothing.
.. where can I gen a deeper insight on this? .. knowing exactly how..
 
I dug out my original '70's mood ring from a box in my desk, where it sat under my Elvis concert ticket stub - either my mood has grown very dark with age, or the ring no longer works. :smile: But it was instructive, with no heat and/or non-functioning liquid crystal material (not sure why it no longer functions), the ring is dark, meaning all the incident light is absorbed - probably by a backing material that is black, which means that the incident light is transmitted through the faux-stone and through the crystal layer. If the liquid forms a periodic array as it should, then some light wavelengths will reflect while the rest transmit to the black layer and are absorbed. The periodicity changes with temperature, so the apparent reflected color changes with temperature.
 
Edi said:
Well. that explains pretty much nothing.
.. where can I gen a deeper insight on this? .. knowing exactly how..

What part of absorption don't you understand? We can help you better if you be more specific. If you just want a general introduction to absorption, it would be more productive to read the http://en.wikipedia.org/wiki/Absorption_%28electromagnetic_radiation%29" article than for me to retype it here.
 
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Mood Rings contain thermochromic elements. Mood ring color changes in response to the body temperature.
 

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