Are there materials that can change the amount of light passing through? For example due to aligning their molecules or crystals differently?

In my materials book there are sometimes notes to some awesome materials. Like ones that change properties when electricity runs through them or that slowly transition into new structures due to heat.

So I was wondering if there are materials that have the property to change the amount of light passing through. For example that become more transparent or more opaque when a current runs through it, a magnet is used to change the alligning of the molecules/crystals or due to heat.


2 Answers 2


Yes, there are different ways to achieve this. The transmission of electrochromic glass depends on voltage. Photochromic glass (darkening in sunlight) is used in some eyeglasses.

You can also consider liquid crystal displays between crossed polarizers.

So your question is quite broad. For more information see the entry Smart glass on wikipedia and links there.


I believe that nearly any material that has mass can change the amount of light that passes through since light is does not possess mass itself

  • 1
    $\begingroup$ The OP is asking whether a material can change its transparency in a certain band, which has nothing to do with the masslessness of light. $\endgroup$ Mar 6, 2018 at 22:24
  • $\begingroup$ More to the point, the OP means change over time. As in, is there any material whose transmittance will change in response to some external input. $\endgroup$ Mar 6, 2018 at 23:14
  • $\begingroup$ I missed that, apologies $\endgroup$
    – C. Jordan
    Mar 13, 2018 at 16:52

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